psychometric (version 2.4)

Est.true: Estimation of a True Score

Description

Given the mean and reliability of a test, this function estimates the true score based on an observed score. The estimation is accounting for regression to the mean

Usage

Est.true(obs, mx, rxx)

Value

Estimated True score

Arguments

obs

an observed score on test x

mx

mean of test x

rxx

reliability of test x

Author

Thomas D. Fletcher

Details

The estimated true score (that) is computed as
that <- mx*(1-rxx)+rxx*obs
When the obs score is much higher than the mean, the that < obs
When the obs score is much lower than the mean, that > obs

References

Dudek, F. J. (1979). The continuing misinterpretation of the standard error of measurement. Psychological Bulletin, 86, 335-337.

See Also

CI.tscore, SE.Est

Examples

# Examples from Dudek (1979)
# Suppose a test has mean = 500, SD = 100 rxx = .9
# If an individual scores 700 on the test
Est.true(700, 500, .9)

# If an individual scores 400 on the test
Est.true(400, 500, .9)