In a Recent Round of Layoffs in a Company, the Percent

In a recent round of layoffs in a company, the percent of employees 50 and older who were laid off was much higher than the percent younger than 50 who were laid off. However, when the data were analyzed separately in each job category, the percent of employees 50 and older who were laid off was lower than the percent of employees younger than 50 who were laid off in each job category. This reversal of direction of the association between age and being laid off, when job category is taken into account, is called:

A) Simpson's paradox.
B) least-squares regression.
C) negative association.
D) a residual plot.