This study attempted to better define the nature of critical thinking and its component skills (with a focus on the interpretation, analysis, and evaluation of data) by investigating the relationship between critical thinking competency and an activity card method of instruction, individual or small group work patterns, achievement, and sex. The propaganda techniques found in magazine advertisements were selected by the researcher as a valid curriculum stimulus for the critical thinking of fifth graders. Eighty fifth-grade students in one elementary school were divided equally into two experimental classes exposed to the activity card treatment and two control classes involved in noncritical thinking activities of equal duration. Each was further divided into either an individual or a small group pattern of interaction with the activity card treatment on nontreatment activities. A pretest and posttest design was followed. Interactions between the method of instruction, grouping pattern, and sex were insignificant except in the case of interactions between the boys and small group learning, which was significant. The researcher concluded that affective factors are involved in growth in critical thinking as well as intelligence and achievement. (Author/LL)