# I need assistance with a R studios assignment. I have attached the files containing the data.

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I need assistance with a R studios assignment. I have attached the files containing the data.

I need assistance with a R studios assignment. I have attached the files containing the data.

1 PSYC 4001 4 Advanced Research Methods in Psychology Supplementary Exam: Semester 1, 202 2 Available : 18 July 202 2 at 8am AEST Due : 21 July 202 2 at 11:59pm . Absolutely no late exams accepted so submit as you go! Questions : 30 Word count : 2000 Total marks: 50 Pages : 14 Hello everyone! This is the description for the exam , which is due on Canvas on July 21st , 202 2 at 11:59pm . You’ll need to submit a Word -knitted version of the completed R Markdown file found in this zip file, according to the following instructions: 1. Rename the document called exam .Rmd as studentID -exam .Rmd. (Replace studentID with your student ID number). This is your R Markdown file, where you’ll be putting all your code and answers. Replace “Your name, Student ID” in the header of the R Markdown file with your name and student ID. (Keep the quotes) 2. While we encourage collaboration in tutorials and learning in general, you should not be collaborating with anybody AT ALL for this assignment. That means sharing code priva tely or publicly; even talking in the abstract about problems will effectively be collusion. You should be completing it independently, with no help from any other person in any capacity. Of course, as always, you are free to use any of the resources from the class to help you, and you’re also free to google or look anything up that you like (as long as you aren’t asking anybody, including anybody on discussion boards, specific questions about this assignment, and everything you write is in your own words). Different people will be getting different datasets and thus may have different answers even on the same questions anyway. 3. Plagiarism check is enabled and you can check the similarity report on your submission. In previous years we have found people who tried to cheat, so please don’t risk it! That said, understand that we will not be naively looking at the overall % figure: with this sort of assignment a certain amount overlap is inevitable, so don’t worry if you get what looks like a high % score. Pr obably most people will. We will be using the plagiarism check for the parts of the assignment where we’d expect some variability, and to give a general sense of the overall gestalt. 4. Complete all of the problems below in the R Markdown document. Do not change any of the arguments to the code chunks, like the names of the code chunks or where it says echo=FALSE or whatever. If a problem asks you to display a tibble or variable so it shows up in the knitted version, make sure that you do as the marker can not evaluate it without seeing it, and if they can’t see it then they won’t be able to award you points for it! Remember that to display a tibble (or any variable) you just type its name on a line of its own within the R chunk. 5. I’ve structured this so that, as much as possible, questions do not build on each other. That means that if, say, you can’t get Q5 then you can still get Q6. Try to do all of them. 6. Go for partial credit! Many of these questions have some form of partial credit possible. What that means is that if it is asking for some R code, break down the problem into pieces. Even if you can only do some of the pieces, or do them part of the way, that will be worth something. [Note that there is no question -by -question rubric available becau se designing one would mean giving away the answers. In general we will give full credit for responses that correctly address all of the parts of the question.] Short answer questions (SAQs) are also worth partial credit and are generally asking for some thoughtful interpretation. If it is based on a previous graph or test you’ve done, if you did the first part wrong but discuss it well, you can still get most or all points for the SAQ part. If your code does not run but you want to include it for possible partial credit, just comment it out (using the # sign) so that it shows up in the knitted document. If you include a lot of commented -out code and some is correct and some isn’t, we will not give you credit for the commented -out code; put the thing in ther e that you think is the closest to the correct answer, don’t just include everything. 2 7. We are not overly worried about to what decimal place you round answers to and unless the problem explicitly specifies what you should round to, you will not lose cre dit for this unless you round so much that your answer is impossible to discern (e.g., don’t round p-values to the nearest integer! ). Similarly, you will not lose points for trivial presentation things like using parentheses instead of commas around statis tical references, as long it’s clear. That said, for those who want a guideline, I’ll suggest that you follow APA format or round p-values to three decimal places, degrees of freedom to one, and test statistics and probabilities to two. 8. If the question is an SAQ, it specifies a word count. Unfortunately , there is no way that I know of in R Markdown to do a word count. You need to either calculate it from the knitted document, or type up your answer in Word 1 and then cut and paste it into the R Markdown file . (Please put your answer in between the word ANSWER and [Word count: XX]; needless to say, those two bits do not count towards your word count.) The word counts I’ve specified in each question are designed to give you a guideline about the number of words you shoul d need answer completely and correctly . So don’t feel like you must use all of the words; if you can answer it fully with less, that’s fine. It’s okay to go over the word limit for individual questions as long as the total word count for all of the questio ns is under 2200 words (i.e., 2000 +10%, with the standard penalty if it is 2000 + 10% or higher 2; there is no penalty for having fewer words than 2000 -10% ). Also, if a question hasn’t specified a word count then you don’t need to include it in your total word count ; these are questions that require very few words so it’s not worth the effort. 9. There is no word count for code chunks. Word count only applies to the SAQs. Remember to report your total word count for the assignment as a whole at the top of the document. Your total word count is the sum of the word counts for all of the SAQ s. 10. You’ll be turning in the knitted output of your R Markdown file. We prefer that you knit to Word but if you can’t get Word to knit then html is okay. In the worst case, you can turn in the completed Rmd file. We highly, highly recommend that you knit as you go: (a) knitting can identify problems in your code that you would have otherwise missed; and (b) you do not want to get close to the deadline and think you’re done only to find that you’re having troubles knitting. Save yourself the panic and knit often. 11. Similarly, you can turn in the exam multiple times, so please turn it in even before it’s perfectly polished . That will save you last -minute panic or computer issues. Also, take a screenshot for proof of having turned it in just in case you need it. If you do not submit your exam by the due date we cannot accept it no matter what so just submit as you go! We will only mark the most recent submission so you lose nothing by doing so. The story For the exam, we return to Bunnyland and Otherland one year later! When we last saw them things had come to a tentative conclusion but substantial challenges remained. Could people from both lands manage to work together to solve their food problem? Would tensions flare? Would the fragile peace get disrupted? Would they be able to grow enough food that nobody went hungry? You’ll find answ ers to these questions in the vignettes below. We’ll visit each of our friends and see what they’re doing and you’ll be able to help them with their statistics one last time. Enjoy! * * * 1 I know different software calculates word count in slightly different ways, so we are using Word as the standard. 2 The penalty is as detailed in the student manual: “10% of the total marks available for a given assessment task will be deducted for every 10% that the word count exceeds the word limit specified for the task ”. So up to 2,199 results in no penalty. Betwee n 2,200 and 2,399 is a 10% deduction, between 2,400 and 2,599 is 20%, and so forth. 3 Punk music The last year has been a good one for Flopsy . They have embraced their non -binary identity and decided to change their name and pronouns to something that felt more like “them”. They are now known as Flaye and have formed a goth punk band along with their new friend from Otherland, Sissily the snake . They’ve spent much of the last year touring around with their band, which is called Mental Limit Theorem. There is one main venue in Bunnyland (called Bunnystadia) and one main venue in Otherland (called Markov Chain) that they play at. After a while, Flaye and Sissily begin to wonder what factors affect concert attendance the most. They therefore examine the last 120 concerts (60 at Bunnystadia and 60 at Markov Chain). Half of the concerts in each location (30 concerts) had Flaye as the headline singer and half had Sissily. This data can be found in the df tibble, which has been loaded for you. Each row consists of one concert . There are four columns: concert : Random code corresponding to each concert location : Whether that concert was in Bunnystadia or Markov Chain singer : Whether the headline singer that night was Flaye or Sissily attendance : Number of people at that concert Flaye and Sissily want to know what factors affect attendance. Is it the venue they are in, which of the two of them is the headline singer for that concert, or an interaction of the two? Q1 [3% of total marks] First, as always, let’s visualise the data. In the code chunk for this question make a bar plot showing the attendance for eac h concert . You should have two panels, one corresponding to Bunnystadia and one for Markov Chain . Within each panel, the re should be two bars, one for each headline singer. The two bars within each panel should be semi -transparent and of different colours (not the default) and should show the mean attendance for concerts headlined by Flaye and Sissily respectively (with error bars corresponding to standard error) and individual data points in the same colour as the bars. Your figure should have no legend, a title, informative axis labels, and a nice theme. Q2 [6% of total marks] For simplicity let’s assume that all the assumptions of the relevant statistical test have been met, so you don’t have to evaluate them. Instead, run the appropriate statistical test to eva luate Flaye and Sissily’s research question and report on the results in 120 words or less. In your report, don’t worry about descriptive statistics but do include an explanation of which statistical test you used, the appropriate stats reference, and the interpretation of this data in terms of the research question. Don’t worry about effect size or any post -hoc tests. END OF SECTION 4 Fun with Quackers Not much has changed for Cuddly Paws, although all the drama made her think even more about what she wanted out of life. She hadn’t enjoyed all of the tension and worry but had enjoyed how everything had forced her out of her shell a bit and deepened her interactions with people. Though she still preferred the comforts of art over people, she did expand out of her comfort zone enough to start making friends . Over time, one surprising friend stood out to her: Quackers! His silliness proved to be a nice balan ce against her seriousness and she had a lot of fun with him. Over time she started wondering what factors led her to have the most fun with him, so she started tracking it. She had an intuition that both the amount of rain each day might matter, as well as Quacker’s mood, and thought that the two factors might also interact with each other. She therefore tracked this over the course of a few months. The data can be found in the dq tibble , which has been loaded. Each row corresponds to the data from one day. There are four columns: day : What day it was (day1 in February, day80 in late April) rain : The amount of rain that day in millimeters qmood : Quacker’s mood that day (0 = very sad; 50= very happy) fun : The amount of fun Cuddly Paws ha d that day (0 = none; 50 = maximum possible) Cuddly Paw’s research question is wh at factors (if any) predict how much fun she had: the amount of rain that day, Quacker’s mood that day, and/or an interaction of the two. Your job in the next few problems is to use your R and statistics knowledge to find the answer to this question. Q3 [7% of total marks] Run the appropriate statistical test to evaluate the research hypothesis , assuming for now that no assump tions have been violated. Report on the results in 170 words or less. In your report, don’t worry about including descriptive statistics but do include an explanation of which statistical test you used, the predictor and outcome variables, the stats refere nce, and the interpretation of this data in terms of the research question. Include effect size and report an interpretation of all the significant unstandardised coefficients except the interaction. 3 Don’t worry about calculating or reporting standardised coefficients. Q4 [6% of total marks] There are four assumptions we discussed in lectures that you should check for the test you just ran . Check them in the four code chunk s (the order does n’t matter) . For each, indicate what you checked, what the results indicate (with stats reference if there is one) , and how you can tell. Use no more than 180 words total for this entire question. Q5 [5% of total marks] Given the results in Q3 and Q4, what would you do to answer this research question? You may use the code chunk to make any figure(s) you think necessary to figure out what is going on. You do not need to perform any additional tests or analyses, but you sh ould say what you think is going on as well as you would do and why if you were in this situation in real life. This could include describing any additional analyses that you would perform and how they would support different conclusions. Use no more than 240 words. [Note: this is a challenging question and you are being asked to critically think about the data and the rest of the process. Marks depend primarily on the clarity, appropriateness, and thoroughness of your discussion. There are multiple ways to earn full credit.] END OF SECTION 3 To be clear, you should run and evaluate the model with the interaction; just do not report on the interpretation of the coefficient of the interaction here (whether it is significant or not). We do this for simplicity and to save on word count. 5 Psychology Following the events of a year ago, Bunny achieved her dream and became a psychologist. She also grew to be good friends with Foxy, having been impressed by the empathy and courage that became visible during her adventures in Otherland. That adventure and the bond with Bunny gradually led Foxy to come out of her shell more, sharing more about her upbringing in far -away Foxland. Upon graduating with her degree, Bunny and Foxy decided to open up a psychological practice, with Bunny as the psychologist and Fox y as the manager. Soon their practice — called Hearts and Minds — became central to helping the people of Bunnyland and Otherland begin to process the years of slow trauma caused by increasing hunger, fear, and uncertainty. And both Bunny and Foxy grew greatly in confidence, having faced so many of their biggest fears (including statistics and R). After a while Foxy notices that she and Bunny vary in what kind of therapies they tend to feel most comfortable doing. She looks up the records for the client s who finished all of their sessions, and notes the kind of therapy that worked for each client (ACT or CBT) as well as which of them was the therapist for that person. The data can be found in the table called psychTable , which has been created for you in the code chunk for Q6. It is also shown below. Foxy would like to know if she and Bunny differ in the distribution of the therapies they have used. Q6 [3% of total marks] Run the appropriate statistical test to evaluate Foxy’s question and report on the results in 80 words or less. In your report, don’t worry about including descriptive statistics , but do include an explanation of which statistical test you used and why, th e appropriate stats reference, and the interpretation of this data in terms of the research question. Don’t worry about effect size. END OF SECTION 6 Meatball Cafe The opening up of relations between Bunnyland and Otherland has been great for Gladly. He hadn’t realised how hard he found it as one of the few bears in a land full of bunnies until things changed. He ended up making fast friends with Super Size, who also had struggled with a similar alienation being so large and different. He was still large and different, but with Gladly that didn’t seem to matter, and the two bonded over one of their favourite topics: food. Now that they were growing so much more food , both Gladly and Super Size’s persistent hunger was assuaged, and the two friends turned their thoughts to how they could share their love of food with others. One day Gladly had an idea: they could start a restaurant! It was ideal for both of them. They could be around friends all day, and make use of all of the fantastic new foods being grown . Before long, their restaurant was the social hub linking Bunnyland and Otherland. Located on the border, Meatball Cafe was a vibrant place of food, conversation, and laughter. No longer did Gladly wonder what he wanted to do with his life: he knew! And best of all, there were meatballs every day. After a year, Gladly and Super Size are curious about what season their sales are best in. Fortunately they have tracke d their sales, which can be found in the tibble called dm. It has been loaded for you . Each row consists of one day , and there are three columns: day : unique identifier for each day season : the season that day occurred in (winter, spring, summer, autumn) meatballs : the number of meatballs sold that day Their research question is whether on average the number of meatballs per day sold is the same for every season. Your job is to use your R and statistics knowledge to find the answer to this questio n. Q7 [2% of total marks] First, as always, let’s visualise the data. In the code chunk for this question make the appropriate figure visualizing the meatballs sold for each season . Your figure should show each of the individual data points as well as a different geom displaying a summary for each season , a col our scheme (other than the default) with different colours for each season and the colours of the data points matching the geom , no legend, and of course a title, informative axis labels, and a nice theme. Q8 [2% of total marks] There are several assumptions you could test , but for the sake of simplicity we will focus on the normality assumption (you may presume that homogeneity of variance holds). Evaluate normality using the appropriate test. In 30 words or less, report the statistical test and indicate what the results of the code reveal (including stats reference) . Was the assumption violated? How can you tell? Q9 [4% of total marks] Run the appropriate statistical test to evaluate the research hypothesis given Q8. Report on the results in 60 words or less. In your report, don’t worry about including descriptive statistics but do include an explanation of which statistical test you use d, what the predictor and outcome variables were, the appropriate stats reference, the effect size and its interpretation, and the interpretation of this data in terms of the research question. Q10 [4% of total marks] Perform post -hoc pairwise tests and in 40 words or less, report the tests and which seasons (if any) had significantly lower meatball sales than others, along with their p-values. You do not need to report the non -significant pair s or their p-values. END OF SECTION 7 New leaders The path toward integrating the people of Bunnyland and Otherland was not easy, but was helped a lot by the burgeoning friendship between LFB and Rainbow the unicorn. LFB will always remember Rainbow as her first friend in Othe rland. For her part, Rainbow has found LFB to be a delightful companion and loves her fresh views and honest, straightforward manner. The trust between the two of them carried the day several times when tensions were high. As a result, when it came time for the next elections, there was a groundswell of support for the idea of electing LFB and Rainbow together to be leaders of their respective lands. LFB and Rainbow were more surprised than anyone, but found that they truly enjoyed being able to guide thei r people and work together to make things better. It has now been five months since they were elected and Rainbow and LFB would like to know what factors underlie their support. They therefore commission some surveys in 108 districts. The data is in the dibble dl, which has been loaded for you. Each row corresponds to one district and it has four columns: district : code corresponding to the district in question education : the average level of education in that district (0=lowest, 10=highest) income : the average annual income in that district, in thousands of dollars support : the percent of people in that district who support LFB and rainbow Q1 1 [4% of total marks] Calculate a Pearson correlation between education and income and report the results in 60 words or less. In your report, use the appropriate stats reference and interpret what this result suggests about the relationship between education and income . How does the correlation you found relate to the R2 you would obtain if you ran a regression with education as the outcome and income as the predictor? Q1 2 [5% of total marks] Their main question is about how these variables are related to support and specifically which of them matter, if any. For this we are going to do model selection. For simplicity let’s assume that all assumptions are met. In the code chunk below, create the following three models (you don’t have to show the output, just create them). 1. modelS E: support is the outcome variable, education is the only predictor 2. modelS I: support is the outcome variable, income is the only predictor 3. modelS EI: support is the outcome variable, education and income are both predictors, but there is no interaction Q1 2a. Perform model selection between these three using AIC or BIC (either is fine) as the complexity penalty. In no more than 15 words, state which model is preferred and why (you don’t need to report the AIC/BIC results, just interpret them) . Q1 2b. In no more than 85 words, explain why we use something like AIC or BIC to do model selection, rather than just picking the model that has the highest R2. Q1 3 [6% of total marks] In 130 words or less, report the best -fitting model from Q1 2, including a description of which statistical test you used, your predictor and outcome variables, the appropriate stats references, and the interpretation of the research question in terms of this data. Don’t report effect size or the interpretation of the unstandardised coefficients but do discuss the relative strength of the predictors and why the size of the values of the undstandardised and standardized coefficients are different. END OF SECTION 8 Adventurers His missions to Otherland sparked in Doggie a taste for adventure: while all the other people started settling in and working together, he grew increasingly restless. Moreover, he realised that some early life trauma meant he would probably not be able to trust the Others for a wh ile, so he decided it would be best to heal on his own. He spent more and more time wandering around in the hills nearby, wondering what he wanted to do with his life. On one of these trips he came across Kevin and Kevin Clark (the string), who were feelin g similarly at sea. They got to talking and realised that what they all wanted was to strike out somewhere new — to see what there was to see in the mountains and valleys beyond both Otherland and Bunnyland. They thus decided to give it a try together. Be fore long the three of them gained a reputation far and wide as almost mythical adventuring figures. After a while, Doggie starts to worry that he isn’t as good at adventuring as Kevin is. Since they alternate who leads each other on any given day, Doggi e decides to track how many kilometers they travel on each day. The dataset dd, which has been loaded for you already , contains a list of the last 50 days where each person led the adventures. Each row is one of the days , and there are the following three columns: day : unique identifier for each day person : the per son leading that day (Doggie or Kevin ) distance : the total distance in kilometers they travelled that day Doggie wonders if he and Kevin are significantly different in terms of how far they travelled on days that they led. He hopes to this knowledge to infer whether he is as good as Kevin . Q1 4 [1% of total marks] Check the assumption of normality in the code chunk below. In 40 words or less, report the statistical test and indicate what the results of the code reveal (including stats reference(s)) . Was the assumption violated? How can you tell? Q1 5 [7% of total marks] Run the appropriate statistical test to evaluate the research quest ion and report on the results in 170 words or less. In your report, include descriptive statistics (means, not sd) and effect size (including interpretation) as well as an explanation of which statistical test you used and why , the appropriate stats reference, and the interpretation of this data in terms of the research question. What does this result indicate, if anything, about whether Doggie is as good of an adventure r as Kevin , and why? END OF SECTION 9 Statistical consulting Finally, we get to Shadow and Little Blue. This semester showed both of them how much they love statistics and R, and it showed everyone in Bunnyland and Otherland how valuable statistics and R are when making decisions. As a result, they decided to open a statistical consulting business. Their job is both to collect data but also to answer anybody and everybody’s statistical questions. They are very happy. What follows are a few of the questions they’ve gotten recently. Shadow and Little Blue have gone on leave, so see if you can answer them as well! Q1 6 [5% of total marks] Q1 6a. Which of the following statistical references is impossible? For (i) and (ii) indicate your answer by reporting A or B. Use your knowledge about each test statistic and how it is related to degrees of freedom and p-values to answer this quest ion. You do not need to do any coding. (i) A.χ2ሺ2ሻ= −13.64 ,= .042 or B. χ2ሺ4ሻ= 1.67 ,= .796 (ii) A. t(89.19 ) = -5.95 , p < .001 or B. t(91 ) = 11.82, p = .885 Q1 6b. For each answer in Q1 6a, explain it by describing intuitively what the test statistic captures and thus why you chose the answer you did , making reference to the degrees of freedom and/or p-value as appropriate. Use no more than 130 words in total for this question . Q17 [4% of total marks] Q1 7a. For each of the following equations, indicate which figure on the right it corresponds to. (Note: you do not need to code anything for this problem; just use your understanding about what the various coefficients mean, and pay special attention to the posi tive and negative signs). (i) = 1.51+ (ii) = 1+ 2+ 12+ (iii) = 21− 1.52+ (iv) = 21+ 2− 312+ Q1 7b. For each answer in Q17a, explain why you chose it by discussing the relevant aspects of the equation and how they map onto the figure. You do not need to discuss every single part of the equation and the figure, only the ones that were relevant for distinguishing them. [Note: we are not looking for answe rs of the form “I ruled out all of the other possibilities, so it must be this one ”; although you can mention this if it was part of your reasoning process, each answer must make reference to that equation and the figure in some way]. Use no more than 150 words in total for this question . Q18 [2% of total marks] Quackers has been struggling with statistics – he thinks it is annoying for some reason! – so he decides to ask you one of his questions. “I don’t understand something about non -parametric tests like the Wilcoxon,” he says. “I get that we should use them if assumptions of normality are violated and we can’t use things like the Welch t-test. But why not use them all of the time? If they make fewer assumptions, aren’t they better?” Quacker s goes on, “I asked Shadow and Little Blue about this but they were in a rush and just muttered something about Type 2 error and power, which I didn’t catch. So can you explain it to me, including what power and Type 2 error has to do with it?” You have 110 words or less. 10 Q19 [3% of total marks] Consider all of the figures below . For each of them, explain whether that figure is or is not consistent with obtaining an F statistic less than one on that data . Your answer for each should be either “is consistent” or “is not consistent” and thus does not contribute to the overall word count. END OF SECTION 11 Psychological Assessment Some of these questions require numerical answers only. Don’t delete anything from the Markdown file aside from the "_______" characters which appears in some places, and which indicates a gap which you should fill. Before attempting these questions please ensure that you have studied: - The Week 11 and 12 lectures - The Week 12 tutorial - The Practice Quiz entitled "Revision Quiz for Section 12.3 of Week 12 (Day 2)" - The questions and solutions contained within the document "pa -exam -prep -prompts - solutions.pdf", which is linked from the Exam page of the Canvas website for this subject. Q2 0 [2 % of tota l marks] A treatment for Lazar's Disease is being developed. People participating in a study were randomly selected to receive either the treatment, or else a placebo. Later on, a test was administered to investigate whether they got the disease. 550 peo ple received the treatment and got the disease 450 people received the treatment and didn't get the disease 430 people received the placebo and got the disease 570 people received the placebo and didn't get the disease Produce R code to calculate the Risk Ratio and fill the gaps in the Markdown document . Hint: One gap should be replaced with the word "Placebo", one with the word "Treatment", and one with the Risk Ratio. Report the Risk Ratio, rounded to three decimal places (e.g. 0.991, or 3.120). Q2 1 [2% of total marks] Q21a. Which of the following would most increase your suspicion that you are encountering an instance of the file drawer problem? A. The small studies in your funnel plot have effects that vary to an implausibly low degree, and are spread roughly evenly on each side of the overall average B. The small studies in your funnel plot have effects that vary to an implausibly low degree, and are not spread roughly evenly on each side of the overall average C. The small studies in your funnel plot have effects that vary to an implausibly high degree, and are spread roughly evenly on each side of the overall average D. The small studies in your funnel plot have effects that vary to an implausibly high degree, and are not spread roughly evenly on each side of the overall average Report A, B, C, or D (and nothing else) in the blank provided on the Markdown file. Q21b. Let's say you believe you ha ve encountered the file drawer problem. Briefly describe one action you could take to try to ensure that the file drawer problem does not invalidate your meta -analysis . More than one reasonable approach was discussed in the lecture, but please describe one action only. Use 20 words or fewer. 12 Q2 2 [2 % of total marks] In the Robo -Hungarian Empire the ability to bend metal objects is regarded as an important skill. There is a test of metal -bending ability which has a reliability of .95, a mean of 20, and a standard deviation of 3. Flavia scored 22 on this test. You are a government official within the Robo -Hungarian Empire, and are responsible for making a decision on whether Flavia has showed sufficient skill to gain employment within your department. You are wondering whether we have good grounds for believing that Flavia's metal -bending abilities are above average. Report a 95% Confidence Interval for Flavia’s true score. Give two numerical values: the lower and upper bounds of the Confidence Inter val. Show your workings in the code chunk. Report each value to 3 decimal places, e.g. 99.123. Q23 [1% of total mark s] Your workplace is planning to make important decisions about individuals on the basis of their scores on a test which it has developed . The test consists of 80 items, and its reliability is .88. Your boss knows that this level of reliability does not meet the desirable standard for making important decisions about individuals with respect to specific test scores, and is open to increasing the number of items on the test so as to meet that desirabl e standard. Your boss wants you to provide an estimate of the total number of items the revised test will need to have in order to surpass the desirable standard. Your boss wants the revised version of the test to have as few items as possible, while none theless surpassing the desirable standard. Provide R code to calculate the total number of items that will be required on the revised version of the test. Please note that since fractional items are not possible, you should round your answer in an appropr iate manner so as to satisfy the requirements of the question. You should either report your answer as an integer, or with only zeros after the decimal place. Hint: Your answer must necessarily be higher than 80, since the original test already has 80 items. Q2 4 [2% of total marks] You understand that increasing the number of items is not the only way to improve the reliability of a test. Suggest two other ideas which would have the effect of increasing the reliability of the test. Please label your ideas "Idea 1:" and "Idea 2:". Suggest only ideas that were addressed in the lecture, and don't suggest increasing the number of items, as we already covered that idea in Q23. Respond in 50 words or fewer. Q2 5 [4% of total marks] There is a disorder named Glossop’s Disorder. Individuals over 40 years of age often develop serious symptoms as a result of Glossop's Disorder. We will not discuss these symptoms in full here, but they include things such as developing a tendency to put random words in “quotation ” marks when writing, as well as a tendency to inappropriately end sentences with ellipses... In young peopl e between the ages of 18 and 25 the only known symptom of Glossop's Disorder is that individuals with the disorder tend to sleep for 9 to 12 hours per night on average. The majority of young people who average 9 to 12 hours of sleep per night do not have Glossop's Disorder. However, the majority of young people with Glossop's Disorder average 9 to 12 hours of sleep per night. 13 A test for Glossop’s Disorder has been developed, and a trial was done in which the test was applied to 100,000 randomly selected 21 -year -old members of the population. The trial results showed: 95 true positives (people who were criterion positive, test positive) 220 false positives (people who were criterion negative, test positive) 99680 true negatives (people who were criterion neg ative, test negative) 5 false negatives (people who were criterion positive, test negative) Give a numerical answer to each of questions in part (a) -(d). Express all these numerical values as percentages, with each percentage reported to three decimal places (e.g. 99.123%). Use the code chunks to show the calculations for each. Q2 5a. What is the test sensitivity? Q2 5b. What is the test specificity? Q2 5c. What is the test Positive Predictive Power? Q2 5d. What is the test Negative Predictive Po wer? Q2 6 [2 % of total marks] This question relates to the situation and data described in Q2 5. You are a specialist in sleep disorders, and in that context a 21 -year -old named Alexei has been referred to you. Alexei is concerned because over a prolong ed period he has been sleeping 11 hours per night on average. You administer the test for Glossop's Disorder to Alexei, and he tests positive. In 30 words or fewer, do you estimate that the probability Alexei has Glossop’s Disorder is - higher than the test Positive Predictive Power stated in your answer to Q2 5c - lower than the test Positive Predictive Power stated in your answer to Q2 5c - the same as the test Positive Predictive Power stated in your answer to Q2 5c In your answer you must re-state one of these three options and also briefly explain the reasoning behind your answer. Q2 7 [1 % of total mark s] You are a practitioner and are choosing between the following two tests Test A: 51.000% sensitivity, 97.001% specificity Test B: 96.000% sensitivity, 97.000% specificity In the context in which you find yourself, the key goal of testing is to "rule in" the presence of the disease, by which we mean to obtain strong evidence that the disease is present. The reason why it's important to "rule in" the presence of the disease is that persons who test positive will be selected for additional procedures. These additional procedures are quite invasive and expensive, and it's important that they are not unnecessarily applied to people who are free of the disease. With that goal in mind, which test would be the better one for you to choose, Test A or Test B? For the purposes of this question you won't have any access to any other information about the test, even though such information would have been potentially helpful - thus, for example, you won't have data on PPP, NPP, or prevalence. For this question, the only possible answers are "We shoul d prefer Test A" or "We should prefer Test B", and you should not explain the reasons for your preference. 14 Q2 8 [1 % of total mark s] Imagine that you are taking a university subject with a stated aim of covering French history during the period 1800 -1919, with one decade covered in each week of the course. The only assessment for the subject is an exam in which you are required to write an essay on one decade of your own choosing (so, for example, you might choose to write about French history du ring the years 1880 - 1889). What is the term for the threat to validity that is posed by the scenario described above? Answer in 10 words or fewer. Q2 9 [3 % of total marks] Within the context of a Multitrait -Multimethod Matrix, consider the following two correlations: Correlation A. Correlation between self -report measure of impulsivity and interviewer rating measure of impulsivity. Correlation B. Correlation between interviewer rating measure of social skill and acquaintance report measure of impulsivity. Q2 9a. Would you prefer that Correlation A is higher than Correlation B, or that Correlation B is higher than Correlation A, or that the two correlations are about the same? The only permissible answers here are "I would prefer Correlation A be higher than Corre lation B", "I would prefer Correlation B be higher than Correlation A", or "I would prefer that both correlations are about the same". Therefore you must answer in exactly 10 words. Q2 9b. What sources of variance does each correlation (i.e. Correlation A and Correlation B) relate to? Answer in 70 words or fewer. Q30 [1 % of total mark s] This is a freebie - as long as you say anything, you will get full credit! Who was your favourite character in Bunnyland or Otherland, and why? END OF EXAM

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