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The Edinburgh Handedness Inventory (EHI) was administered to 600 students from two urban secondary schools and two universities. The respondents were categorized by age (three groups) and sex. The questionnaire was re‐administered to a sample of 69 respondents after an interval of 4 weeks. Principal axes factor analysis of the test and retest data showed the EHI to have a single factor which exhibited a high stability over the test‐retest time period. However, one item (the use of scissors) was relatively unstable in relation to the derived (handedness) factor. A simple factor structure was also extracted from each ‘age × sex’ data set. The handedness factor showed a high stability across both age and sex. However, three items (knife, broom and box‐lid) did not load well on the handedness factor and were generally unstable in relation to this factor. When assessing handedness with this questionnaire it is recommended that responses to particular items be weighted according to their stability and their contribution to the handedness factor. Alternative scoring procedures would seriously affect the otherwise high validity that this questionnaire has for assessing handedness.
McFarland et al. (Fri,) studied this question.