Experimental Designs Answers

A therapist wants to study the effects of yoga and meditation on stress relief. She has 60 volunteers who experience varying levels of stress. Half of the participants will be assigned to practice yoga for one month and the other half will practice meditation. Before the experiment begins, all of the participants will be asked to rate their stress levels on a scale from 0 to 10, with 0 representing "no stress” and 10 representing "highest level of stress.” The therapist believes that current stress levels could affect the results; therefore, she has the subjects participate in both treatments. For each subject, a coin is flipped. If it lands on heads, then the subject will practice yoga for the first half of the month and meditation for the last half of the month. If it lands on tails, the subject will practice meditation for the first half of the month and yoga for the last half. Stress levels are measured before switching treatments and again at the end of the month. The differences in stress levels will be compared.

A therapist wants to study the effects of yoga and meditation on stress relief. She has 60 volunteers who experience varying levels of stress. Half of the participants will be assigned to practice yoga for one month and the other half will practice meditation. Before the experiment begins, all of the participants will be asked to rate their stress levels on a scale from 0 to 10, with 0 representing "no stress” and 10 representing "highest level of stress.” At the end of one month, the participants will be asked to rate their stress level again. The differences in stress levels will be compared.

A shoe company wants to test an updated model of a running shoe on its wear after one month of running. They recruit 50 people who run on a regular basis to participate in the study. They will have the runners wear the shoes when they run for two months. After two months, the wear on the shoes will be determined using the depth of the tread and flexibility of the toe box. The wear between the new model and the original model will then be compared. The company decides to use a matched pairs design and devises two options.Option A: The 50 subjects are paired based on running ability. The fastest two runners are paired together, the next fastest two, etc. For each pair of runners, the researcher will flip a coin. If the coin lands on heads, then the first runner will receive the new model of shoes and the second runner will receive the original model. If the coin lands on tails, the first runner will receive the original model of shoes and the second runner will receive the new model. After 2 months of use, the difference in wear for the pairs of runners will be determined.Option B: The 50 subjects will each receive both models of shoes. At the beginning, the runner will flip a coin, and if it lands on heads, they will wear the new model on their right foot and the original model on their left foot. Then after one month, they will change and use the new model on their left foot and the original model on their right foot. After the second month, the wear for each model will be determined and compared for the 50 runners.

A veterinarian knows that the supplement glucosamine is beneficial for dogs’ joints. He wants to determine if a supplement with both glucosamine and chondroitin would be more beneficial than glucosamine alone for dogs’ joint health. The veterinarian asks the owners of dogs with known joint issues if they would be willing to have their dog participate in his study, and 32 owners agree to the study. Sixteen dogs are randomly assigned to the glucosamine group and the remaining 16 are assigned to the glucosamine with chondroitin group. After 6 months, the dogs’ joint health is measured for each treatment and compared. The results of the study were inconclusive and the veterinarian decides to do the experiment again. He gets 24 volunteers and decides that he needs to use a randomized block design.