Feedback is one of the most powerful influences on learning and achievement, but this impact can be either positive or negative. Its power is frequently mentioned in articles about learning and teaching, but surprisingly few recent studies have systematically investigated its meaning. This article provides a conceptual analysis of feedback and reviews the evidence related to its impact on learning and achievement. This evidence shows that although feedback is among the major influences, the type of feedback and the way it is given can be differentially effective. A model of feedback is then proposed that identifies the particular properties and circumstances that make it effective, and some typically thorny issues are discussed, including the timing of feedback and the effects of positive and negative feedback. Finally, this analysis is used to suggest ways in which feedback can be used to enhance its effectiveness in classrooms.

Various methods for determining unidimensionality are reviewed and the rationale of these methods is assessed. Indices based on answer patterns, reliability, components and factor analysis, and latent traits are reviewed. It is shown that many of the indices lack a rationale, and that many are adjustments of a previous index to take into account some criticisms of it. After reviewing many indices, it is suggested that those based on the size of residuals after fitting a twoor three-parameter latent trait model may be the most useful to detect unidimensionality. An attempt is made to clarify the term unidimensional, and it is shown how it differs from other terms often used interchangeably such as reliability, internal consistency, and homogeneity. Reliability is defined as the ratio of true score variance to observed score variance. Internal consistency denotes a group of methods that are intended to estimate reliability, are based on the variances and the covariances of test items, and depend on only one administration of a test. Homogeneity seems to refer more specifically to the similarity of the item correlations, but the term is often used as a synonym for unidimensionality. The usefulness of the terms internal consistency and homogeneity is questioned. Unidimensionality is defined as the existence of one latent trait underlying the data.

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The purpose of this meta-analysis is to examine the effects of adventure programs on a diverse array of outcomes such as self concept, locus of control, and leadership. The meta-analysis was based on 1,728 effect sizes drawn from 151 unique samples from 96 studies, and the average effect size at the end of the programs was .34. In a remarkable contrast to most educational research, these short-term or immediate gains were followed by substantial additional gains between the end of the program and follow-up assessments ( ES = .17). The effect sizes varied substantially according the particular program and outcome and improved as the length of the program and the ages of participants increased. Too little is known, however, about why adventure programs work most effectively.

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