Intervention for Dyslexia - The British Dyslexia Association

Before the results are summarised a methodological point must be noted. In the
following paragraph various average standard scores are quoted from the reports of the
study, all of which are in the range 94 to 107 and therefore appear to be well within the
average range – which would be surprising for children stated to be the lowest
achievers. The explanation is that standard scores for these children were not calculated
in the usual way, from the nationally established norms for the tests, but within the
samples. This is said to provide greater statistical power (because otherwise
standardised scores could not have been calculated for the children who had zero raw
scores at the outset, i.e. most of the sample, except by the very rough-and-ready
method of attributing them a standardised score one less than the lowest figure in the
conversion table). However, this procedure does mean that the ‘standard scores’ quoted
are not quite what they seem and need to be interpreted with care. It also means that
the effect sizes given may not be equivalent to those that would have been derived from
normal standardised scores. It would have been helpful to the profession if normal
standardised scores had also been published, to facilitate comparisons with other
programmes.
That said, the study found that, at the end of the year, Year 1 classes in the ECaR
schools (the whole classes, not just the children receiving the programme) had gained
slightly in average WRaPS standard score (from 100 to 102.5), whereas the Year 1
classes in the non-ECaR schools had declined slightly (from 100 to 97). The difference
between the groups at the end of the year was statistically significant (p