Chapter 3.2, Problem 73E

To determine

To find: the slope of regression line

Answer to Problem 73E

The slope of the regression line will be negative, that is less than 0.

Explanation of Solution

Given:

1. Will be greater than 0.
2. Will be less than 0.
3. Will be equal to 0.
4. You can’t perform regression on these data.
5. You can’t tell without seeing the data.

It is known that smokers don't live as long (on average) as non-smokers, and heavy smokers don't live as long as light smokers. Assume that a least-square regression experiment is performed on the age at death of a group of male smokers, Y and the number of packs per day they smoked, X.

It is clear that as the number of packs per day smoked increases, the age number of survival days) will be decreases.

That is, as X increases, Y decreases. In other words, there exists a negative correlation between X and Y. We know that the sign of the slope is same as the sign of correlation coefficient. Hence, we can say that the slope of the regression line would be negative.

Conclusion: Hence, the slope of the regression line will be negative, that is less than 0.