Refer to given Case Study, "Kids and Weight Lifting." Did the experiment described there use a completely randomized design, a matched-pair design, or a randomized block design? Explain.
Case Study
Kids and Weight Lifting
Read the original source on the companion website, https://www.cengage.com/ statistics/Utts4e.
Is weight training good for children? If so, is it better for them to lift heavy weights for a few repetitions or to lift moderate weights a larger number of times? Researchers at the University of Massachusetts set out to answer this question with a randomized experiment using 43 young volunteers between the ages of 5.2 and 11.8 years old. The children, recruited from a YMCA after-school program, were randomly assigned to one of three groups.
Group 1 performed 6 to 8 repetitions with a heavy load, Group 2 performed 13 to 15 repetitions with a moderate load, and Group 3 was a control group. Figure 6.3 illustrates the process used in this study. The steps for this randomized experiment include recruiting volunteers to participate, randomly assigning participants to the three groups, carrying out the weight-lifting treatments (the explanatory variable), and comparing muscular strength and endurance (the response variables) for the three groups.
The exercises were performed twice a week for 8 weeks. According to the research report, the higher-repetition, moderate-load group (Group 2) showed the best results. Here is a sample of the results:
Leg extension strength significantly increased in both exercise groups compared with that in the control subjects. Increases of 31.0% and 40.9%, respectively, for the low repetition- heavy load and high repetition- moderate load groups were observed (Faigenbaum et al., 1999, p. e5).
Because the children were randomly assigned to the exercise groups, they should have been similar, on average, before the weight-training intervention. Therefore, it is reasonable to conclude that the different training programs actually caused the difference in results.