STAT 200 Assignment Summer 2017 Term 2 Please attach a cover sheet (posted on Connect) when you hand in the assignment. Due: Wednesday July 19 at 1pm in the STAT200 dropbox in ESB (No late homework will be accepted) Total marks: 30 marks Instructions: • Typewritten answers are preferred. If your handwriting is illegible or if the answers are not presented in a neat and organized manner, with answers clearly numbered you may lose marks. • For question 1: – You may use R Commander to plot graphs and obtain summary statistics – You must attach all plots when you hand in the assignment and ensure that all your graphs are labelled appropriately. 1. A sample of college students performed skills tests to measure cognitive function, completed a survey that asked many questions about attitudes and habits, and kept a sleep diary to record time and quality of sleep over a two week period. The dataset contains 253 observations on the following 27 variables: Gender 1=male, 0=female ClassYear Year in school, 1=first year, ..., 4=senior LarkOwl Early riser or night owl? Lark, Neither, or Owl NumEarlyClass Number of classes per week before 9 am EarlyClass Indicator for any early classes GPA Grade point average (0-4 scale) ClassesMissed Number of classes missed in a semester CognitionZscore Z-score on a test of cognitive skills PoorSleepQuality Measure of sleep quality (higher values are poorer sleep) DepressionScore Measure of degree of depression AnxietyScore Measure of amount of anxiety StressScore Measure of amount of stress DepressionStatus Coded depression score: normal, moderate, or severe AnxietyStatus Coded anxiety score: normal, moderate, or severe Stress Coded stress score: normal or high DASScore Combined score for depression, anxiety and stress Happiness Measure of degree of happiness AlcoholUse Self-reported: Abstain, Light, Moderate, or Heavy Drinks Number of alcoholic drinks per week WeekdayBed Average weekday bedtime (24.0=midnight) WeekdayRise Average weekday rise time (8.0=8 am) WeekdaySleep Average hours of sleep on weekdays WeekendBed Average weekend bedtime (24.0=midnight) WeekendRise Average weekend rise time (8.0=8 am) WeekendSleep Average weekend bedtime (24.0=midnight) AverageSleep Average hours of sleep for all days AllNighter Had an all-nighter this semester? 1=yes, 0=no 1 Use the dataset SleepStudy.txt to answer the following questions: (a) Construct a histogram of the number of classes missed in a semester for the college students. Describe the shape of the distribution. Report only one measure of center and one measure of spread that are appropriate for summarizing the data. Any inappropriate statistics provided may result in a deduction of marks. [3 marks] (b) Provide an appropriate graphical display for comparing the distributions of GPA between different categories of self-reported alchol use. Provide a brief interpretation of the graph. Compare both the center and the spread of the distributions. Select only one measure of centre and one measure of spread for the comparison. Are there any outliers present? [4 marks] (c) Examine the relationship between quality of sleep and happiness of the college students. (i) Provide the appropriate statistic and plot to examine the relationship between these two variables. Comment on the pattern and strength of the relationship. [3 marks] (ii) Based on our results in part (i), can we conclude that better quality sleep causes college students to be happier? Why or why not? [2 marks] (d) The researcher wants to predict the college students’ GPA from scores on the test of cognitive skills. (i) Fit a least squares regression line that predicts the college students’ GPA from scores on the test of cognitive skills. Write down the equation of the regression line. [1 mark] (ii) Provide an interpretation of the slope of your regression line in the context of the question. [2 marks] (iii) Use the fitted regression line to predict the GPA for a student who has a Cognition Z score of: A. 0.5 B. 4.0. Do you have any concerns about these predictions? Briefly justify your concerns (if any). [3 marks] (iii) Draw appropriate plot(s) to assess the adequacy of the linear fit in part (i). Is the fit adequate? Justify your answer. [2 marks] 2. Two hundred adults shopping at a supermarket were asked about the highest level of education they had completed and their smoking habits. Results are summarized in the table. Smoker Non-smoker Total High school 32 61 93 2 yr college 5 17 22 4+ yr college 13 72 85 Total 50 150 200 (a) Find the marginal distribution of smoking status. [2 marks] (b) What percent of shoppers were smokers with high school as their highest level of education? [1 mark] (c) What percent of the smokers had high school as their highest level of education? [1 mark] (d) Among shoppers with high school as their highest level of eduction, what percent were smokers? [1 mark] (e) Create a segmented bar graph comparing education level among smokers and non-smokers. Label your graph clearly. Percentage should be on the y-axis. [2 marks] (f) Do these data suggest there is an association between smoking and education level? Give statistical evidence to support your conclusion. [3 marks] 2

• 1502813866-SleepStudy.txt

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Status NEW Posted 15 Aug 2017 04:08 PM My Price 8.00

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