Comparing differences in Dyslexia Index dimensions between research subgroups

I have been exploring Dyslexia Index on a dimension by dimension basis as part of the process of trying to explain what is responsible for the significant differences in Academic Behavioural Confidence between the three research subgroups of particular interest (that is, RG: ND-400, DI-600, DNI – students with no evidence of dyslexia, students with disclosed dyslexia and with a Dx >592.5, students with unidentified dyslexia-like profiles and with a Dx > 592.5, respectively).

There is more work to do here, but in this first report is found a summary data table which presents the mean values for each research subgroup in each of the 20 dimensions which together comprise the Dyslexia Index metric that I have devised for this project.

For many, if not most of the dimensions, the very significant ‘face value’ differences between these mean values for RG: ND-400 and RG: DI-600 are confirmed as statistically significant at p-value levels, which are off the scale, with equally large Hedges’ ‘g’ effect sizes. The full data table is linked to the graphic ->

However, the outcomes that emerge when research groups DNI and DI-600 are compared on this dimension-by-dimension basis allow an important conclusion to be drawn. In 15 out of the 20 dyslexia dimensions the mean values for each of the dimensions respectively are very similar between each of the research subgroups. This is telling me that where these dimensions are clear indicators of ‘dyslexia-ness’ in identified dyslexics, given that similar outcomes are apparent in the research subgroup of ‘suspected’ dyslexics that have been previously unidentified, these dimensions are indeed suggesting that the unidentified dyslexics are indeed dyslexic. This is a gratifying result and adds further construct validity to the Dyslexia Index metric that has been devised for this project as a mechanism for discriminating students who may be dyslexic amongst the research group of students who declared no dyslexia.

Additionally, it is interesting to note the dimensions where differences between the mean values are apparent.

The most noticeable of these differences fall into two distinct categories:

  1. dimensions associated with challenges in learning to read and apparently continued anxiety about reading out loud; these are dimensions:
    • ‘my spelling is generally weak’
    • ‘in my writing at school I often mixed up similar letters’
    • ‘I get really anxious when asked to read out loud’
  2. dimensions associated with visuo-spatial awareness, specifically dimensions:
    • ‘I get my ‘lefts’ and ‘rights’ easily mixed up’
    • ‘I find following directions to get to places quite straightforward’

I will return to this later to include these interesting new features of the data analysis into the Discussion section of the final thesis, but in the meantime, the data summary table is recorded here, not least so that I can recall what I did when I come to more formally write it up.

Leave a Reply