A study was conducted with the objective of determining the effect of two different strength-training programs,one involving the use of a balance ball and the other using stationary exercise equipment,on blood pressure and cholesterol levels in women over the age of 60.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 8 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 8 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)matched pairs design.
B)design involving blocking.
C)designed experiment that failed because it had systematic bias.
D)double-blind randomized experiment.
E)randomized experiment with two factors: type of exercise and type of medical measurement.

Question

Quizplus · Accepted Answer

This is a double-blind randomized experiment because both the experimenter and the medical technician were unaware of which group the subjects were assigned to. This helps to eliminate bias and increase the validity of the results. The use of two different strength-training programs, blood pressure and cholesterol levels as the response variables, and a randomly assigned treatment group make this a well-designed experiment. A matched pairs design would involve each subject being their own control, and a design involving blocking would involve dividing the subjects into subgroups based on some pre-determined characteristic. Systematic bias was not evident in this experiment. There were two factors, but they were not both manipulated; one was a subject characteristic (age) and the other was the type of exercise program.

A Study Was Conducted with the Objective of Determining the Effect