A study was conducted to determine whether exercise or dietary supplements would slow bone loss in older women. An investigator measured the mineral content of bones by photon absorptiometry. A total of 6 measurements (3 on dominant side and 3 on nondominant side) were made on each subject at the beginning of the study. The researcher then assigned the subjects to the two treatments and conducted the experiment. When it was time to conduct the analysis the researcher decided to check on whether there was a difference in bone mineral content prior to assignment to a group. What type of test would be used to check for a difference?