Insight Psychometrics Technical Manual - Canadian Test Centre

the confidence bounds are relatively wide. But gI combines those and has 90items and the confidence interval is relatively narrower.In interpreting this analysis, the following points should be kept in mind:1. This is a group-administered test where all examinees take the sameitems (except that different levels are used for grades 2–3, 4–5, and6–7). Conventional individually-administered tests are often effectivelymore accurate when variable starting points and discontinue pointsallow focus on an individual’s ability.2. The traits being evaluated are (approximately) normally distributed sothat large differences in percentile consequently occur with smalldifferences in tested measurements in the centre of the distribution.That is where the widest confidence intervals are found, but it is just aconsequence of there being, in fact, little measurable differencebetween individuals who are at, say, the 40 th and 60 th percentiles. Thisis true for both group-administered and individually-administeredassessments.Figure 18: Example of graph of NPR confidence bounds17