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Clinical Trials and Differences in Mean of HDL Levels in Groups

6. A clinical trial is run to assess the effects of different forms of regular exercise on HDL levels in
persons between the ages of 18 and 29. Participants in the study are randomly assigned to one of
three exercise groups - Weight training, Aerobic exercise or Stretching/Yoga and instructed to
follow the program for 8 weeks. Their HDL levels are measured after 8 weeks and are summarized
below.

Exercise Group is Weight Training, N = 20 Mean = 49.7 Std Dev = 10.2
Exercise Group is Aerobic Exercise, N =20 Mean = 43.1 Std Dev = 11.1
Exercise Group is Stretching/Yoga, N = 20 Mean = 57.0 Std Dev = 12.5

Is there a significant difference in mean HDL levels among the exercise groups? Run the test at a
5% level of significance. HINT: SSwithin = 21,860.

7. Consider again the data in problem #6. Suppose that in the aerobic exercise group we also
measured the number of hours of aerobic exercise per week and the mean is 5.2 hours with a
standard deviation of 2.1 hours. The sample correlation is -0.42.

a) Is there evidence of a significant correlation between number of hours of exercise per week and
HDL cholesterol level? Run the test at a 5% level of significance.
b) Estimate the equation of the regression line that best describes the relationship between number
of hours of exercise per week and HDL cholesterol level (Assume that the dependent variable
is HDL level).
c) Estimate the HDL level for a person who exercises 7 hours per week.
d) Estimate the HDL level for a person who does not exercise.

Solution Preview

Please see the attached file.

6. We are given the following information:

Group1 Group2 Group3
Size
20 20 20
Mean
49.70 43.10 57.00
Standard Deviation 10.20 11.10 12.50

Within (Error) Sum of Squares = 21860

We want to examine whether there exist significant difference in mean HDL levels among the three groups at 5% level of significance.
For this we can use ANOVA one-way classification.
The null hypothesis is There is no significant difference in mean HDL levels among the three groups.
Alternative hypothesis There is significant difference in mean HDL levels among the three groups.
Combined mean = = 49.93
Between (Treatment) Sum of Squares =
...

Solution Summary

The clinical trails and differences in mean of HDL levels in groups.

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