A study was conducted with the object of determining the effect on blood pressure and cholesterol levels in women over the age of 60 of two different strength-training programs, one involving the use of a balance ball and the other using stationary exercise equipment. Eighty women over the age of 60 were identified and randomly divided into two equal-sized experimental groups. Each member of the two groups was trained and allowed to follow the prescribed routine for eight weeks. The subjects were aware of the purpose of the study but not that there were two different treatment groups involved. The cholesterol levels and blood pressure for subjects were measured at the start and at the end of the eight weeks. The experimenter and the medical technician were not told to which group any of the subjects were assigned. This is an example of an attempt to conduct A) a randomized experiment with two factors: type of exercise and type of medical measurement
B) a double-blind randomized experiment.
C) a matched-pairs design.
D) a design involving blocking
E) a designed experiment that failed because it had systematic bias.