Abstract: This study focused on the effects that a person's sex and appearance have on ratings of his or her credibility. Specifically, it is an examination of differences in ratings of expertise, character, and dynamism of male and female sources who appeared as experts in simulated television interviews, and whether variations in clothing affect perceptions of credibility of males and females differently. A stimulus videotape was created in which male and female actors posing as college professors appeared in three modes of dress: conservative, causal, and neutral. Subjects drawn from a sample of college students and from a civic organization comprised mostly of adults over age 35 viewed the interviews and rated the sources according to characteristics which measured source expertise, character, and dynamism. Contrary to expectations, no significant differences were found between expertise and character ratings of male and female sources. However, male sources were rated as more dynamic. Credibility ratings of female sources were expected to be significantly lower when they were dressed casually than when dressed conservatively. No significant difference in ratings betwee the two dress conditions for females were found. It was also predicted that subjects Dissertation Discovery Company and the University of Florida are dedicated to making scholarly works more discoverable and accessible throughout the world. This dissertation, "Effects of Sex and Appearance on Ratings of Source Credibility" by Erika Engstrom, was obtained from the University of Florida and is being sold with permission from the author. A free digital copy of this work may also be found in the university's institutional repository, the IR@UF. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation.