Schafer and Graham* discuss a hypothetical study in which blood pressure is measured at two time points. Assume that all subjects’ blood pressures were measured at the first time point. Now assume...

Schafer and Graham* discuss a hypothetical study in which blood pressure is measured at two time points. Assume that all subjects’ blood pressures were measured at the first time point. Now assume that some subjects did not return to have their blood pressure measured at the second time point. List the three primary missing data mechanisms discussed in this chapter, define them (both in terms of probability statements and a plain English definition), and apply each to the blood pressure example to explain how the subjects’ blood pressure data could become missing at the second measurement occasion.