Resenhoeft, Villo, and Wiseman (2008) conducted a study showing that a woman shown in a photograph was judged as less attractive when the photograph showed a visible tattoo compared to the same photograph with the tattoo removed. Suppose a similar experiment is conducted as a repeated-measures study. A sample of n = 12 males looks at a set of 30 photographs of women and rates the attractiveness of each woman using a 5-point scale (5 = most positive). One photograph appears twice in the set, once with a tattoo and once with the tattoo removed. For each participant, the researcher records the difference between the two ratings of the same photograph. On average, the photograph without the tattoo is rated MDD = 1.2 points higher than the photograph with the tattoo, with SS = 33 for the difference scores.
Does the presence of a visible tattoo have a significant effect on the attractiveness ratings? Use a two-tailed test with α = .05.