Strack, Martin, and Stepper (1988) reported that people rate cartoons as funnier when holding a pen in their teeth (which forced them to smile) than when holding a pen in their lips (which forced them to frown). A researcher attempted to replicate this result using a sample of n = 25 adults between the ages of 40 and 45. For each person, the researcher recorded the difference between the rating obtained while smiling and the rating obtained while frowning. On average the cartoons were rated as funnier when the participants were smiling, with an average difference of MD = 1.6 with SS = 150.
a. Do the data indicate that the cartoons are rated significantly funnier when the participants are smiling? Use a one-tailed test with a = .01.
b. Compute r2 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.