Abstract
This study examined the stability of reading difficulties (RD) from grades 2 to 6 and focused on the effects of measurement error and cut-off selection in the identification of RD and its stability with the use of simulations. It addressed methodological limitations of prior studies by (a) applying a model-based simulation analysis to examine the effects of measurement error and cut-offs in the identification of RD, (b) analyzing a non-English and larger sample, and (c) examining RD in both reading fluency and reading comprehension. Reading fluency and reading comprehension of 1,432 Finnish-speaking children were assessed in grades 2 and 6. In addition to the use of single cut-off points on observed data, we used a simulation approach based on an estimated structural equation model (SEM) in order to examine the effect of measurement error on RD identification stability. We also examined the effect of single cut-offs by using a simulation-based buffer zone. Our results showed that measurement error affects the identification of RD over time. The use of a simulation-based buffer zone could control both the effects of measurement error and the arbitrariness of single cut-offs and lead to more accurate classification into RD groups, especially for those with scores close to the cut-offs. However, even after controlling for measurement error and using buffer zones, RD was not stable over time for all children, but both resolving and late-emerging groups existed. The findings suggest that reading development needs to be followed closely beyond the early grades and that reading instruction should be planned according to individual needs at specific time points. There is a clear need for further consideration of the mechanisms underlying the stability and instability of RD.
Highlights
Studies on reading difficulties (RD) have mainly focused on reading development during the early grades, and long-term longitudinal follow-up studies are scarce
We examined whether RD identification was stable over time even if we control for measurement error and the use of single cut-offs
The findings highlight that measurement error affects the accurate identification of children with RD by causing misclassifications and that the simplicity of the single cut-offs can contribute to false impressions on instability of RD over time
Summary
Studies on reading difficulties (RD) have mainly focused on reading development during the early grades, and long-term longitudinal follow-up studies are scarce. Stability of Reading Difficulties reading skills in later grades despite RD being identified during early grades) and those with late-emerging RD (i.e., RD identified during the later grades despite normal early reading skills) (e.g., Catts et al, 2012; Torppa et al, 2015; Etmanskie et al, 2016). These unstable groups are of particular interest because they may provide more understanding on the developmental risk and supportive mechanisms in RD. Do these groups truly exist, or are they a result of measurement error? When we categorize continuous reading distribution at two time points using arbitrary cut-offs, is it possible that the changes in RD classification are due to measurement error?
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