A researcher sought to determine whether women’s feelings about their body are affected by subliminal presentations of very thin body images. Presentation of an image for 15 milliseconds (msec) is too fast for people to be aware of the image, making it “subliminal” or outside of conscious awareness.

Women (N = 60) were asked to participate in an experiment described as “speed of judging words on a computer screen.” Neutral words (not related to body image) were presented at the center of the screen for 3 sec and participants pressed the left shift key if the word appeared in uppercase letters, and the right shift key if the word appeared in lowercase. All participants viewed the same words, half in uppercase and half in lowercase letters (randomized). However, for a random half of the trials an image was presented for 15 msec before the word appeared. Participants were randomly assigned to see thin images of women (T), overweight women (O), or neutral objects (N), such as a book or houseplant. Women in each group viewed only one type of image. In each condition of 20 participants, women viewed 50 images. After finishing the computer task, participants completed several questionnaires, including a measure of body dissatisfaction. The women were asked to select from an array of seven line drawings of female figures (from very thin to very obese) the drawing that illustrated how they would like to appear (ideal) and the drawing that best represented how they perceived themselves (actual). The number of figures between the ideal and actual is an operational definition of body dissatisfaction (with 0 indicating no dissatisfaction, negative scores indicating a desire to be thinner, and positive scores indicating a desire to be heavier). The mean body dissatisfaction score for the Thin Image group was –1.25 ( SD = 1.07), the mean score for the Overweight Image group was –0.75 ( SD = 1.16), and the mean score for the Neutral Image group was –0.20 ( SD = .83).

A. Identify the design of this study, including the independent and dependent variables. Explain why the researcher asked participants to judge the same neutral words in each condition, and provide examples of factors the researcher controlled by using random assignment to conditions.

B. How would you describe the effect of the independent variable using the means for each condition? What do the standard deviations tell you about the body dissatisfaction ratings in the experiment?

C. The p value for the F -test for the effect of the type of image is p 5 .009. What claim would you make about the effect of the independent variable based on this probability?

D. The .95 confidence interval (CI) for the thin condition is –1.71 to –0.79; the CI for the overweight condition is –1.21 to –0.29; and the CI for the neutral condition is –0.66 to 0.26. What claim would you make based on the estimates of the population means for the three groups in the experiment based on a comparison of these confi dence intervals?

E. The effect size for the difference between the means for the thin and neutral groups is d = .85. What information does this effect size tell you about subliminal exposure to thin images compared to neutral images, beyond what you know from the test of statistical significance and from comparing confidence intervals?