# Validation of Rapid

Validity is the extent to which a test measures what it claims to be measuring and appropriate inferences can be made from the test score. There are a variety of methods used in estimating the validity of a test. Construct validity relates to how well the test measures the intended construct and one way of assessing this involves comparison of mean scores of groups for which score differences would be expected. For Rapid, this analysis looks at the differences between dyslexic and non-dyslexic students for each subtest (see Table 11). This analysis indicates effects on all subtests, with non-dyslexics outperforming dyslexic students. Note that this analysis does not include students within the 4–7-year-old age range as only a very small proportion of dyslexic students are diagnosed prior to the age of 8.

Table 11. Construct validity

 Subtest Group N Mean SD SE of Mean Cohen’s d* Mobile phone Dyslexic Non-dyslexic 71 2088 95.48 100.95 12.867 14.992 1.527 0.328 0.39 Funny words (Non-words) Dyslexic Non-dyslexic 73 2067 93.59 100.05 11.499 15.195 1.346 0.334 0.48 Word chopping (Segments) Dyslexic Non-dyslexic 63 1846 92.35 99.94 12.364 15.146 1.558 0.353 0.55 Mobile phone (11-15) Dyslexic Non-dyslexic 13 1576 100.23 103.60 9.833 14.580 2.727 0.367 0.27 Non-words (11-15) Dyslexic Non-dyslexic 16 1738 93.13 103.80 13.185 14.606 3.296 0.350 0.77 Segments (11-15) Dyslexic Non-dyslexic 15 1664 97.60 103.97 12.304 14.524 3.177 0.356 0.47

* Cohen’s d is a measure of effect size of the difference between two means