Question Format Is the Best Predictor of Item Discrimination: A Multivariable Analysis
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| Title: | Question Format Is the Best Predictor of Item Discrimination: A Multivariable Analysis |
|---|---|
| Language: | English |
| Authors: | Kirk Hillsley (ORCID |
| Source: | Journal of Microbiology & Biology Education. 2025 26(3). |
| Availability: | American Society for Microbiology. 1752 N Street NW, Washington, DC 20036. Tel: 202-737-3600; e-mail: journals@asmusa.org; Web site: https://journals.asm.org/journal/jmbe |
| Peer Reviewed: | Y |
| Page Count: | 12 |
| Publication Date: | 2025 |
| Document Type: | Journal Articles Reports - Research |
| Education Level: | Higher Education Postsecondary Education |
| Descriptors: | Test Items, Test Format, Biology, Science Tests, Scores, Undergraduate Study, Foreign Countries, Difficulty Level, Item Banks |
| Geographic Terms: | Canada |
| ISSN: | 1935-7877 1935-7885 |
| Abstract: | Item discrimination, the point-biserial correlation between performance on a question and total exam score, was analyzed in relation to question format, difficulty, and Bloom's taxonomy, which are rarely studied together in a joint framework. To estimate their independent contributions in undergraduate biology examinations, simultaneous multivariable linear and logistic models were conducted on an upper year biology item bank (n = 754). Predictors were question format (multiple-choice question [MCQ], short answer [SA], true/false [TF]), difficulty (easy >80%, moderate 60%-80%, hard <60%), and Bloom (recall, understanding, application, analysis). Question format was the strongest independent predictor. Relative to MCQs, SA items showed higher discrimination and greater odds of meeting the ≥0.35 threshold (odds ratio [OR] = 4.18), while TF items were less discriminating (OR = 0.58). Moderate and hard items exceeded easy questions (ORs = 2.75 and 2.45, respectively). For Bloom, higher-order items outperformed recall questions overall; both understanding and analysis items discriminated better than recall items (ORs = 1.4 and 3.56, respectively). A post hoc grouping of moderate difficulty questions showed that SA + higher-order items (0.53) exceeded MCQ + recall items (0.35), with 89% vs 53% of these items, respectively, meeting a discrimination threshold of ≥0.35. In simultaneous models, question format was the strongest independent predictor of item discrimination, moderate difficulty optimized discrimination, and higher-order objectives exceeded recall. These results provide exploratory insights from a single-institution case study and suggest that adding some higher-order short-answer questions of moderate difficulty may represent a pragmatic strategy for improving assessment quality. |
| Abstractor: | As Provided |
| Entry Date: | 2026 |
| Accession Number: | EJ1504782 |
| Database: | ERIC |
| Abstract: | Item discrimination, the point-biserial correlation between performance on a question and total exam score, was analyzed in relation to question format, difficulty, and Bloom's taxonomy, which are rarely studied together in a joint framework. To estimate their independent contributions in undergraduate biology examinations, simultaneous multivariable linear and logistic models were conducted on an upper year biology item bank (n = 754). Predictors were question format (multiple-choice question [MCQ], short answer [SA], true/false [TF]), difficulty (easy >80%, moderate 60%-80%, hard <60%), and Bloom (recall, understanding, application, analysis). Question format was the strongest independent predictor. Relative to MCQs, SA items showed higher discrimination and greater odds of meeting the ≥0.35 threshold (odds ratio [OR] = 4.18), while TF items were less discriminating (OR = 0.58). Moderate and hard items exceeded easy questions (ORs = 2.75 and 2.45, respectively). For Bloom, higher-order items outperformed recall questions overall; both understanding and analysis items discriminated better than recall items (ORs = 1.4 and 3.56, respectively). A post hoc grouping of moderate difficulty questions showed that SA + higher-order items (0.53) exceeded MCQ + recall items (0.35), with 89% vs 53% of these items, respectively, meeting a discrimination threshold of ≥0.35. In simultaneous models, question format was the strongest independent predictor of item discrimination, moderate difficulty optimized discrimination, and higher-order objectives exceeded recall. These results provide exploratory insights from a single-institution case study and suggest that adding some higher-order short-answer questions of moderate difficulty may represent a pragmatic strategy for improving assessment quality. |
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| ISSN: | 1935-7877 1935-7885 |
