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Example
5
Unobserved Variables
Introduction
This example demonstrates a regression analysis with unobserved variables.
About the Data
The variables in the previous example were surely unreliable to some degree. The fact
that the reliability of performance is unknown presents a minor problem when it
comes to interpreting the fact that the predictors account for only 39.9% of the
variance of performance. If the test were extremely unreliable, that fact in itself would
explain why the performance score could not be predicted accurately. Unreliability of
the predictors, on the other hand, presents a more serious problem because it can lead
to biased estimates of regression weights.
The present example, based on Rock, et al. (1977), will assess the reliabilities of
the four tests included in the previous analysis. It will also obtain estimates of
regression weights for perfectly reliable, hypothetical versions of the four tests. Rock,
et al. re-examined the data of Warren, White, and Fuller (1974) that were discussed
in the previous example. This time, each test was randomly split into two halves, and
each half was scored separately.