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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:

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.

The summary table shows data for Dyslexia Index (Dx) and corresponding Academic Behavioural Confidence (ABC) for each of the 5 research subgroups (see explanatory notes below). The most significant feature that emerges from this summary table is the comparison of Academic Behavioural Confidence levels for the two most interesting research subgroups: that is group 'DNI' - student with no previously identified indication of dyslexia, and group 'DI-600' - students with an identified dyslexia and a Dyslexia Index of Dx > 592.5.
The Effect Size difference reported at the foot of the summary table is Hedges' 'g' for Academic Behavioural Confidence, as is the independent samples means t-test result.
These results together are indicating a moderate effect size between ABC for these key, research groups together with a statistically significant difference at the 5% level between the sample mean ABC values.

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

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.

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 detailed explanation of this results summary table.