In Exercises 21–24, refer to the data in the table below. The entries are white blood cell counts (1000 cells,ML) and red blood cell counts (million cells,ML) from male subjects examined as part of a large health study conducted by the National Center for Health Statistics. The data are matched, so that the first subject has a white blood cell count of 8.7 and a red blood cell count of 4.91, and so on.

Subject

	1	2	3	4	5
White	8.7	5.9	7.3	6.2	5.9
Red	4.91	5.59	4.44	4.8	5.17

Context Given that the data are matched and considering the units of the data, does it make sense to use the difference between each white blood cell count and the corresponding red blood cell count? Why or why not?

Five paired observations were recorded from five subjects for the study. The values of white and red blood cell counts were obtained from each of the subjects.

A matched data records multiple information from one experimental unit. In this study, white and red blood cell counts belong to the same subject.

A study is meaningful or makes sense if it can be used for some practical benefit.

In other words, if the result is projected onto the population, it could be used for some purpose.

Evaluating the difference between the red and white blood cell counts is of no practical use in the study. Establishing the differences between the counts will not be helpful to the population.

Thus, the study for the differences between the counts of the two types of blood cells does not make any sense.