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Data coding in SPSS

Research groups and subgroups are designated according to Dylsexia Index boundary values - rationale detailed here and on the project StudyBlog. For quick reference, the table below indicates these groups and subgroups and their respective coding label in SPSS:

Research Group SPSS category code Research SubGroup SPSS category code Criteria
ND 0 ND-400 10 students in research group ND who present a Dyslexia Index Dx < 400
NDx400 90 students in research group ND who present a Dyslexia Index 400 < Dx <592.5
DNI 20 students in research group ND who present a Dyslexia Index Dx > 592.5 - this is the group of greatest interest
DI 1 DI-600 21 students in research group DI who present a Dyslexia Index Dx > 592.5 - this is essentially my 'control' group
DIx600 91 students in research group DI who present a Dyslexia Index Dx <592.5

 

Data summary

The first table (below) is the dataset summary built from 166(good)/183 datasets received. the 17 'spoiled' datasets were discarded because the questionnaires submitted by those respondents were substantially incomplete.

More comprehensive summary tables will be presented here in due course. A deeper critique is currently available on the StudyBlog, particularly discussing internal consistency reliability (Cronbach's α) and the Principal Compenent Analysis conducted on the metrics ABC and Dx

results summary
Explanatory notes:

  • eQNR responses self-sorted into the two, primary Research Groups:
    • DI - students who identified themselves as presenting Dyslexia. This is RG:DI and 68 eQNR responses were received.
    • ND - students indicating that they had no learning challenges or had learning challenges other than dyslexia. This is RG:ND and 98 eQNR responses were received.
  • Research Group: DNI is a subgroup of RG:ND and these students were identified through the Dyslexia Index (Dx) value that their replies generated. The boundary point for skimming these responses was Dx = 600.
  • A second subgroup of RG:ND has been established and this is students who presented a Dyslexia Index of Dx < 400. This subgroup is labelled RG:ND-400. Comparisons will be made against this subgroup as students presenting this low Dx value can be safely considered as presenting very low levels of dyslexic attributes - that is, they do not present a dyslexic learning difference.
  • Datasets from RG:DNI will be compared with datasets from RG:DI which present a Dyslexia Index of Dx > 600 (and this subgroup of RG:DI is designated RG:DI-600), and datasets in RG:ND-400.

Confidence intervals for Dyslexia Index population means

The summary table below presents a comparative overview of summary data for the research groups and subgroups that includes 95% and 99% confidence interval values for the respective population mean Dx values.

confidence intervals for population means


Principal Component Analysis, effect sizes and t-test summary

The summary table below presents an outcome summary of PCA conducted on the two principal metrics: ABC and Dx - refer to the StudyBlog for a more comprehensive commentary but briefly, the table shows the ABC effect sizes between research subgroups ND-400 and DI-600 but particularly between research subgroups DNI and DI-600.

The effect size values are Hedges 'g' results obtained between ABC mean values when the datasets are sifted according to the Dyslexia Index Factor criteria. For example, looking at the row of data for Dx20 5-factor 2: Thinking & Processing, the effect size value of 0.43 shown in the column for ABC24 5-factor: Engagement, indicates the effect size between the ABC means for the factor 'Engagement' when the datasets are sifted according to Dx values established ONLY according to the Dx factor 'Thinking & Processing'. The effect size value of 0.43 in this grid square does NOT indicate the effect size between the Dx factor 'Thinking & Processing' and the ABC factor 'Engagement'. Refer to the StudyBlog for a more detail explanation of this results summary table.

effect size results from PCA