摘要：This article provides an illustrative description of the pre-post difference index (PPDI), a simple, nontechnical yet robust tool for examining the instructional sensitivity of assessment items. Extension educators often design pretest-posttest instruments to assess the impact of their curricula on participants' knowledge and understanding of the concepts taught. Although the use of pretests and posttests is common in Extension evaluation, the validity and reliability of these tests are rarely reported or discussed, mostly due to many Extension educators' limited knowledge of various statistical methods. The PPDI method described in this article should be a useful addition to Extension educators' evaluation toolboxes.
关键词：pre-post difference index ; program evaluation ; pretest-posttest
