Question 1 The most accurate way to determine a persons body

Question 1

The most accurate way to determine a person\'s body fat percentage is to immerse that person in water. Researchers hoping to find an easier way to get a good estimate of body fat percentage immersed 20 male subjects and also measured their waists (in inches). Based on this data, they fit a least-squares regression line, using waist measurement as the explanatory variable:

                                       body fat percentage = - 62.6 + 2.22 X waist.

Choose the response below that best describes how this line should be interpreted.

For every additional inch of waist girth, a person\'s body fat percentage goes up by about 2.22 percentage points on average.

The negative number on the right side of the equation means that the association between body fat percentage and waist measurement is negative.

This line is obviously incorrect because it predicts that someone with a 0 inch waist would have - 62.6 % body fat.

If you measure someone\'s waist, you can predict exactly what his body fat percentage is using this equation.

20 points   

Question 2

Use the regression line for predicting body fat percentage from waist measurement, given in problem #1 above, to predict the body fat percentage of a male with a 40 inch waist. Give your answer to one decimal place. (Enter the number only,e.g., 15.2)

Solution

For every additional inch of waist girth, a person\'s body fat percentage goes up by about 2.22 percentage points on average.

Q2)

                                       body fat percentage = - 62.6 + 2.22 X waist.

body fat % = -62.6 + 2.22 * 40

body fat % = 26.2 %