Question

A possible lurking variable that is most likely accounting for a strong positive correlation between the independent variable of "amount spent on public education" and the dependent variable "amount spent on prison-related expenses" over the past 20 years is

Choose one of the following:

A)Increase in the crime rate over the 20-year period

B)Increase in the amount spent per pupil over the 20-year period

C)The failure of public education in America

D)Increase in population over the 20-year period

Answer 1

Option D: Increase in population over a 20-Year period

Clearly if 20 year ago the education expense was (say x $) then we can’t expect the same expense after 20 years since population is increasing significantly.

Similarly amount spent on prison related activity will be higher if the number of prisoners are higher. Now in 20 years, number of prisoners is expected to increase (well, generally) if the population has increased significantly.

So both of these variables are correlated with Increase in population and if that variable is missing, we’re possibly seeing an spurious correlation betweenn “Amount spent on public education” and “Amount spent on prison-related expenses”.

Thanks