This article refutes a recent claim that computer-based tests produce biased scores for very proficient test takers who make mistakes on one or two initial items and that the "bias" can be reduced by using a four-parameter IRT model. Because the same effect occurs with pattern scores on nonadaptive tests, the effect results from IRT scoring, not from adaptive testing. Because very proficient test takers rarely err on items of middle difficulty, the so-called bias is one of selective data analysis. Furthermore, the apparently large score penalty for one error on an otherwise perfect response pattern is shown to result from the relative stretching of the IRT scale at very high and very low proficiencies. The recommended use of a four-parameter IRT model is shown to have drawbacks. (Contains 6 figures.)