ABSTRACT
The commonly used and most generally useful measure of “test error” is the “error of measurement” defined in Chapters 2 and 3. It is the Standard deviation of the distribution of differences between observed score and true score. However, there are other possible measures of test error that are useful for certain purposes. These measures will be considered in this chapter. The four different types of error are defined as follows: https://www.w3.org/1998/Math/MathML"> e = x − t , https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203052150/a2ba952a-291f-4af7-b1a5-6acb3e41f457/content/math_153_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> https://www.w3.org/1998/Math/MathML"> e = t − r x t ( s t s x ) x , https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203052150/a2ba952a-291f-4af7-b1a5-6acb3e41f457/content/math_154_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> https://www.w3.org/1998/Math/MathML"> d = x 1 − x 2 , https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203052150/a2ba952a-291f-4af7-b1a5-6acb3e41f457/content/math_155_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> https://www.w3.org/1998/Math/MathML"> d = x 1 − r 12 ( s 1 s 2 ) x 2 . https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203052150/a2ba952a-291f-4af7-b1a5-6acb3e41f457/content/math_156_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> Stated in words, these four types of error are:
The difference between true and observed score.
The error made in estimating true score from observed score.
The difference between two observed scores on parallel tests.
The error made in predicting one observed score from the score on a parallel test.
