Robert E. Lana

The Effect of Correlation On the Repeated Measures Design

Abstract : The purpose of this paper is to point out that: (a) any repeated measurements on the same organism will in general exhibit statistical dependence; therefore multivariate analysis of variance rather than univariate analysis of variance is appropriate, and (b) multivariate analysis of variance assumes that the carryover effect of a treatment or a test on succeeding treatments is constant and does not depend on the nature of the succeeding treatment, i.e., carryover is additive and does not interact with succeeding treatments. Most of this paper is concerned with possible experimental and statistical answers to the questions which arise when dependent measures are used in a continuous treatment design. The problem of carryover effects that interact with subsequent treatments is quite different. No answers to this problem are given here; instead we ask if there is, in fact, any way of preserving the advantages of a cross-over design and obtaining unbiased estimates of the treatment effects when carry-over interaction is present.

Subject Awareness and Order Effects in Persuasive Communications

This study was performed with 128 college students acting as Ss. The primary hypothesis that Ss confronted with a hidden pretest in an opinion change study will yield a significant recency effect, and Ss confronted with an exposed pretest will yield a significant primacy effect, was rejected. A primacy effect is in evidence when the pretest is hidden, and no directional effects are present when the pretest is exposed. The secondary hypothesis that a group exposed to a highly controversial topic will yield a significant primacy effect, and a group exposed to a topic of medium controversy will yield a recency effect, or no effect at all, was also rejected.

EXISTING FAMILIARITY AND ORDER OF PRESENTATION OF PERSUASIVE COMMUNICATIONS

Groups who have been familiarized with the topic of a communication or who have had their opinion on a topic tapped by questionnaire, have yielded primacy effects when confronted with opposed communications on the same topic. Two intact groups of Ss, both of which were familiar with the two topics of the communications, were exposed to opposed arguments on various aspects of these topics. There were no significant order effects, nor did either group change opinion regarding their position on the topic. Since no primacy effect resulted, it is concluded that intact groups familiar with a topic may also be committed to a particular position or opinion regarding that topic and hence yield no order effects of any kind.

Fear Arousal and Order of Presentation of Persuasive Communications

94 Ss were exposed to various combinations of fear-arousing and neutral communications concerning the effects of smoking. Measures of anxiety and self-esteem were taken on all Ss with the IPAT Self-analysis Form and the Janis and Field Personality Questionnaire, respectively. Ss were then formed into high and low anxiety and self-esteem groups. Of 24 predicted directions of opinion change, 23 were realized although only 11 were statistically significant. These results were predicted from a fear-reduction interpretation of personality as affecting the susceptibility to persuasion in the situation where opposed communications on the same topic are utilized.

The Inhibitory and Enhancing Influence of Pretest Commitment

Sixty subjects, 30 volunteers and 30 nonvolunteers, participated in an experiment examining pretest sensitization effects. Two interpretations of these effects—the commitment hypothesis and the demand interpretation—are explored. A variation of the Solomon four-group design was employed and an interaction between pretesting and the type of communication used was hypothesized. The hypothesis was confirmed. The possibility of using the GSR as an indicator of sensitivity in the pretest design was further explored. Heightened GSR activity was found for pretested when compared with unpretested subjects.