The answer to the question, "Ability, speed, or both?" may be "both at once" if speed is simply a manifestation of ability. If differences in speed are manifestations of differences in ability, then both speed and ability may reflect a single dimension best characterized by a single score. While measurement of speed has proven…

Data from 181 college students were used to assess whether math reasoning item response times in computerized testing can provide valid and reliable measures of a speed dimension. The alternate forms reliability of the speed dimension was .85. A two-dimensional structural equation model suggests that the speed dimension is related to the accuracy…

If numerical reasoning items are administered under time limits, will two dimensions be required to account for the responses, a numerical ability dimension and a speed dimension? A total of 182 college students answered 74 numerical reasoning items. Every item was taken with and without time limits by half the students. Three psychometric models…