1. Do you view a chocolate bar as delicious or as fattening? Your attitude may depend on your gender. In a study of American college students, Rozin, Bauer, and Catanese (2003) examined the importance of food as a source of pleasure versus concerns about food associated with weight gain and health. The following results are similar to those obtained in the study. The scores are a measure of concern about the negative aspects of eating.
Males Females
n = 9 n = 15
M = 33 M =42
SS= 740 SS =1240
a. Based on these results, is there a significant dif- ference between the attitudes for males and for females? Use a two-tailed test with a = .05.
b. Compute r2, the percentage of variance accounted for by the gender difference, to measure effect size for this study.
c. Write a sentence demonstrating how the result of the hypothesis test and the measure of effect size would appear in a research report.
2. The stimulant Ritalin has been shown to increase at- of attention span of M = 4.8 minutes with a variance tention span and improve academic performance in children with ADHD (Evans et al., 2001). To demon- strate the effectiveness of the drug, a researcher selects a sample of n =20 children diagnosed with the disorder and measures each child's attention span before and after taking the drug. The data show an average increase of s2 =125 for the sample of difference scores.
a. Is this result sufficient to conclude that Ritalin significantly improves attention span? Use a one- tailed test with a = .05.
b. Compute the 80% confidence interval for the mean change in attention span for the population.