We provide a tutorial on differential item functioning (DIF) analysis, an analytic method useful for identifying potentially biased items in assessments. After explaining a number of methodological approaches, we test for gender bias in two scenarios that demonstrate why DIF analysis is crucial for developing assessments, particularly because simply comparing two groups’ total scores can lead to incorrect conclusions about test fairness. First, a significant difference between groups on total scores can exist even when items are not biased, as we illustrate with data collected during the validation of the Homeostasis Concept Inventory. Second, item bias can exist even when the two groups have exactly the same distribution of total scores, as we illustrate with a simulated data set. We also present a brief overview of how DIF analysis has been used in the biology education literature to illustrate the way DIF items need to be reevaluated by content experts to determine whether they should be revised or removed from the assessment. Finally, we conclude by arguing that DIF analysis should be used routinely to evaluate items in developing conceptual assessments. These steps will ensure more equitable—and therefore more valid—scores from conceptual assessments.

Purpose The aim of this study was to compare the effect of four different programmes on spiroergometric, spirometric and clinical parameters in multiple sclerosis (MS) patients. Methods One hundred and twelve MS patients were divided into four groups. The first group underwent neurophysiologically based physiotherapy, the second aerobic training, the third combined therapy (neurophysiologically based physiotherapy and aerobic training) and the fourth did not change any habits. Seventeen patients did not finish the study. Patients were examined on impairment (Expanded Disability Status Scale), disability (Barthel Index), handicap (Environment Status Scale), quality of life (Multiple Sclerosis Quality of Life), fatigue (Modified Fatigue Impact Scale), depression (Beck Depression Inventory Score), respiratory function (spirometric parameters on spirometry) and physical fitness (spiroergometric parameters on a bicycle ergometer). Results The patients who participated in one of our training programmes showed a significant improvement of the examined parameters in comparison to those who did not change their present habits. Each of the four training programmes had a different impact on the parameters, which means that each of them had a different effect. The neurophysiologically based physiotherapy had the greatest impact on impairment, and the aerobic training on spirometric and spiroergometric parameters. All methods (the neurophysiologically based physiotherapy, the aerobic training and the combined programme) had an impact on fatigue.

We present the Homeostasis Concept Inventory (HCI), a 20-item multiple-choice instrument that assesses how well undergraduates understand this critical physiological concept. We used an iterative process to develop a set of questions based on elements in the Homeostasis Concept Framework. This process involved faculty experts and undergraduate students from associate’s colleges, primarily undergraduate institutions, regional and research-intensive universities, and professional schools. Statistical results provided strong evidence for the validity and reliability of the HCI. We found that graduate students performed better than undergraduates, biology majors performed better than nonmajors, and students performed better after receiving instruction about homeostasis. We used differential item analysis to assess whether students from different genders, races/ethnicities, and English language status performed differently on individual items of the HCI. We found no evidence of differential item functioning, suggesting that the items do not incorporate cultural or gender biases that would impact students’ performance on the test. Instructors can use the HCI to guide their teaching and student learning of homeostasis, a core concept of physiology.