Chapter 18, Problem 1QC

Summary Introduction

To determine:

Whether the shortening of the human population over the time is the result of regression towards the mean.

Concept introduction:

Regression towards the mean can be defined as a variable. When it is extremely short or of longer height it is found to be somewhat closer to the average height of a population.

Human height can be measured from head to bottom of the feet. There are several experiments that are carried to see whether human population is getting shorter over time or not. In this case regression of mean is taken in account to check whether height of a population is getting affected or not.

Explanation of Solution

Regression towards the mean is carried to solve the problem that if a parent is of short or long height what would be the next generation; its effect can be observed. This experiment is carried out to see the effect of a parent height on offspring. Sometime it may be also due to environmental factor.

No, regression towards the mean does not imply that the human population is getting shorter. Parent with shorter or longer height will tend to show an average height of a population. When the parent is having a shorter height (average) than the height offspring is more than parent. Similarly when the height (average) of the parent is more than the height (average) of offspring is less than parent.

Conclusion

It is becoming a big question whether a parent height is contributing its child or not, to see or solve this equation regression of mean can be used. From this equation it is clearly seen that if a parent height is extremely short or long the next generation will be closer to the average height of a population.