Detecting Calculator Effects on Item Performance

Abstract

Calculator effects were examined using methods taken from research on differential item functioning. Use of a calculator was controlled on two experimental forms of a test assembled from operational items used on a standardized university mathematics placement test. Results indicated that calculator effects were not present based on analysis of test scores and in only two of the three subscores composed from homogeneous item types. Analyses of item-level functioning indicated, however, that a number of items, including several not included in the two significant subscore combinations, also contained calculator effects. For those items identified, use of the calculator appeared to have changed the actual objective being tested. The findings were generally consistent with previous research: Items that were easier when a calculator was used required either simple computations or use of a function key on the calculator; items that were more difficult required knowledge of a procedure either with or without additional computation. Analysis at the item level facilitated clearer understanding of the impact of calculator use on measurement of the underlying objective.