Which of the Following Will Not Result in Paired Data

Multiple Choice

Which of the following will not result in paired data?

A) The same measurement is taken twice on each person, under different conditions or at different times.
B) Similar individuals are paired before giving the treatments in an experiment. Each member of a pair then receives a different treatment. The same response variable is measured for all individuals.
C) Two different variables are measured for each individual. There is interest in the amount of difference between the two variables.
D) One random sample is taken, and a variable is recorded for each individual, but then units are categorized as belonging to one population or another.