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MET CS 555 Assignment 5 – 20 points

SUBMISSION REQUIREMENTS: Please submit a single document (word or PDF) for submission.  Your submission should contain a summary of your results (and answers to questions asked on the homework) as well as your R code used to generate your results (please append to the end of your submission). Please use R for the calculations whenever possible. You will lose points if you are not utilizing R.  You will also lose 10 points per day for late submissions unless prior arrangements are made with your facilitator.

The data in this document is from 3 groups of students (math, chemistry, and physics) on an IQ related test.  Save the data to excel and read the data into R.  Use this data to address the following questions:

(1) How many students are in each group?  Summarize the data relating to both test score and age by the student group (separately).  Use appropriate numerical and/or graphical summaries. (3 points)

(2) Do the test scores vary by student group?  Perform a one way ANOVA using the aov or Anova function in R to assess.  Use a significance level of α=0.05. Summarize the results using the 5 step procedure.  If the results of the overall model are significant, perform the appropriate pairwise comparisons using Tukey’s procedure to adjust for multiple comparisons and summarize these results.  (7 points )

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(3) Create an appropriate number of dummy variables for student group and re-run the one-way ANOVA using the lm function with the newly created dummy variables.  Set chemistry students as the reference group.  Confirm if the results are the same.  What is the interpretation of the beta estimates from the regression model? (4 points)

(4) Re-do the one-way ANOVA adjusting for age (ANCOVA).  Focus on the output relating to the comparisons of test score by student type.  Explain how this analysis differs from the analysis in step 2 above (not the results but how does this analysis differ in terms of the questions it answers as opposed to the one above).  Did you obtain different results?  Summarize briefly (no need to go through the 5 –step procedure here).   Present the least square means and interpret these.  ( 6 points)

Data set for Assignment 5

group

iq

age

Physics student

34

15

Physics student

33

17

Physics student

32

15

Physics student

25

14

Physics student

36

19

Physics student

30

18

Physics student

31

16

Physics student

34

17

Physics student

29

16

Physics student

34

17

Physics student

39

16

Physics student

33

18

Physics student

39

19

Physics student

42

20

Physics student

41

20

Math student

36

20

Math student

38

28

Math student

37

22

Math student

35

18

Math student

41

19

Math student

40

23

Math student

36

19

Math student

38

16

Math student

24

18

Math student

39

20

Math student

29

19

Math student

38

20

Math student

45

23

Math student

44

24

Math student

44

22

Chemistry student

52

46

Chemistry student

46

38

Chemistry student

51

41

Chemistry student

52

39

Chemistry student

45

44

Chemistry student

49

33

Chemistry student

47

41

Chemistry student

46

36

Chemistry student

41

40

Chemistry student

47

44

Chemistry student

46

46

Chemistry student

42

38

Chemistry student

43

32

Chemistry student

47

41

Chemistry student

40

42