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