Question

A study is done to determine the effects of different forms of regular exercise on HDL levels in persons between the ages of 18 and 29. The forms of exercise observed were aerobic, weight training, and yoga. The participants HDL levels are measured after 8 weeks. Using multiple linear regression, the following regression line was created:

HDL = 54.6-2.22(aerobic exercise)-1.75(weight training)

Aerobic exercise is measured in hours.

Weight training is a dichotomous (binary) outcome. 1=yes; 0=no

Estimate the HDL level for a person who does aerobic exercises for 7 hours per week and does weight training.

Estimate the HDL level for a person who does NO exercise or NO weight training.

The above regression line examines the relationship between aerobic exercises and HDL having adjusted (or controlled) for:

Yoga

Weight training

None of the above

If we compare two patients and one patient completes 2 hours of aerobic exercise a week and the other patient completes 0 hours of aerobic exercise, what is the expected difference in their HDL levels? For this problem assume that both patients are weight training.

Answer 1

Regression Equation:

HDL = 54.6-2.22(aerobic exercise)-1.75(weight training)

Ques: Estimate the HDL level for a person who does aerobic exercises for 7 hours per week and does weight training

Ans:

aerobic exercise = 7 and weight training = 1

Hence, HDL = 54.6 -2.22 * 7 -1.75 * 1 = 37.31

Ques:

Estimate the HDL level for a person who does NO exercise or NO weight

Training

Ans:

aerobic exercise = 0 and weight training = 0

HDL = 54.6 -2.22 * 0 -1.75 * 0 = 54.6

Ques:

The above regression line examines the relationship between aerobic exercises and HDL having adjusted (or controlled) for:

Ans: Yoga

Ques:

If we compare two patients and one patient completes 2 hours of aerobic exercise a week and the other patient completes 0 hours of aerobic exercise, what is the expected difference in their HDL levels? For this problem assume that both patients are weight training.

Ans:

Patient 1: 2 hours of aerobic exercise and weight training = 1

HDL₁ = 54.6 -2.22 * 2 -1.75 * 1 = 48.41

Patient 2: 0 hours of aerobic exercise and weight training = 1

HDL₂ = 54.6 -2.22 * 0 -1.75 * 1 = 52.85

Hence,

Patient 2 – Patient 1 = HDL₂ – HDL₁ = 52.85 – 48.41 = 4.44