1. Participants enter a research study with unique characteristics that product different scores from one person to another. For an independent measures study these individual difference can cause problems. Briefly explain how these problems are eliminated or reduced with a repeated measure.
2. A researcher conducts an experiment comparing two treatment conditions and obtains data with 10 scores for each treatment condition.
a. If the researcher used an independent measures design. How many subjects participated in the experiment?
b. If the researcher used a repeated measures design, how many subjects participated in the experiment?
c. If the researcher used a match subjects design, how many subjects participated in the experiment?
3. Research has shown that losing even one night sleep can have a significant on performance of complex tasks such as a problem solving (Linde& Bergstroem, 1992)To demonstrate this phenomenon a sample of n = 25 college students was given a problem solving task on one day and again at noon on the following day. The students were not permitted any sleep between the two tests. For each student, the difference between the two tests. For each student, the difference between the first and second score was recorded. For this sample the student’s average M0 =4.7 points better on the first test with variance of s2 =64for the difference scores.
a. Do the data indicate a significant change in problem solving ability? Use a two tailed test with a = .05
b. Compute an estimated Cohen’s d to measure the size of the effect.
4. A researcher for a cereal company wanted to demonstrate the health benefits of eating oatmeal. A sample of 9 volunteers was obtained and each participant ate a fixed diet without any oatmeal for 30 days. At the end for the 30 day period, cholesterol was measured for each individual. Then the participants began a second diet except that they added 2 cups of oatmeal each day. After the second 30 day period, cholesterol levels were measured again and the researcher recorded the difference between the tow scores for each participants. For this sample, cholesterol scores averaged M0 =16 points longer with the oatmeal diet with SS = 538 for the different scores.
a. Are the data sufficient to indicate a significant change in cholesterol level? Use the two tailed test with a = .01.
b. Compute r2 the percentage of variance accounted for by the treatment, to measure the size of the treatment effect.
c. Write a sentence describing the outcome of the hypothesis test and the measure of effect size as it would appear in a research report.