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Chapter 11

1. For the each of the following studies determine whether a repeated-measures I test is the appropriate analysis. Explain your answers. a. A researcher is examining the effect of violent video games on behavior by comparing aggressive behaviors for one group who just finished playing a violent game with another group who played a neutral game. b. A researcher is examining the effect of humor on memory by presenting a group of participants with a series of humorous and not humorous sentences and then recording how many of each type of sen- tence is recalled by each participant. c. A researcher is evaluating the effectiveness of a new cholesterol medication by recording the cho- lesterol level for each individual in a sample before they start taking the medication and again after eight weeks with the medication. 3. A researcher conducts an experiment comparing two treatment conditions with 15 scores in each treatment condition. a. If an independent-measures design is used, how many subjects are needed for the experiment? b. If a repeated-measures design is used, how many subjects are needed for the experiment?5. A sample of n = 16 individuals participates in a repeated-measures study that produces a sample mean difference of Mp = 6.45 with SS = 960 for the differ- ence scores.a. Calculate the standard deviation for the sample of difference scores. Briefly explain what is measured by the standard deviation. b. Calculate the estimated standard error for the sample mean difference. Briefly explain what is measured by the estimated standard error.7. The following data are from a repeated-measures study examining the effect of a treatment by measur- ing a group of n = 9 participants before and after they receive the treatment. a. Calculate the difference scores and MD. b. Compute SS, sample variance, and estimated stan- dard error. c. Is there a significant treatment effect? Use a = .05, two tails. Participant Before Treatment After Treatment A B C ARAUJOOUN11. College athletes, especially males, are often per- ceived as having very little interest in the academic side of their college experience. One common prob- lem is class attendance. To address the problem of class attendance, a group of researchers developed and demonstrated a relatively simple but effect tive intervention (Bicard, Lott, Mills, Bicard, & Baylot-Casey, 2012). The researchers asked eachathlete to text his academic counselor "in class" as soon as he arrived at the classroom. The research- ers found significantly better attendance after the students began texting. In a similar study, a researcher monitored class attendance for a sample of n = 16 male athletes during the first three weeks of the semester and recorded the number of minutes that each student was late to class. The athletes were then asked to begin texting their arrival at the classroom and the researcher continued to monitor attendance for another three weeks. For each athlete, the average lateness for the first three weeks and for the second three weeks were calculated, and the difference score was recorded. The data showed that lateness to class decreased by an average of Mo = 21 minutes with SS = 2,940 when the students were texting. a. Use a two-tailed test with a = .01 to determine whether texting produced a significant change in attendance. b. Compute a 95% confidence interval to estimate the mean change in attendance for the population.18. Standardized measures seem to indicate that the average level of anxiety has increased gradually overthe past 50 years (Twenge, 2000). In the 1950s, the average score on the Child Manifest Anxiety Scale was u = 15.1. A sample of n = 16 of today's children produces a mean score of M = 23.3 with SS = 240.b. Make a 90% confidence interval estimate of to- day's population mean level of anxiety.19. Ackerman and Goldsmith (2011) found that students who studied text from printed hardcopy had better test scores than students who studied from text presented on a screen. In a related study, a professor noticed that several students in a large class had purchased the e-book version of the course textbook. For the final exam, the overall average for the entire class was p. = 81.7 but the n = 9 students who used e-books had a mean of M = 77.2 with a standard deviation of s = 5.7.b. Construct the 90% confidence interval to estimate the mean exam score if the entire population used e-books