Page 239 - DMTH404_STATISTICS

Unit 16: Reliability Theory

Notes

Attribute Value —>
This procedure is (theoretically) not concerned with rank orders of respondents, but rather with
the error of estimate for a particular respondent. This technique allows for computerized adaptive
testing.

Item Response Theory - 2

A model for item response as a function of increasing level of subject ability and increasing
levels of item difficulty.
Model 2: the 3 parameter model: Probability of endorsing an item given ability (ø) ,difficulty
(diff), guessing (guessing), and item discrimination sensitivity:
guessing
P(y|ø,diff,guess,sensitivity) = guessing +
1 + esensitivity*(diff-ø)

Attribute value —>
Note that with this model, even though the probability of item endorsement for a particular
item may be a monotonic function of attribute value, item endorsement probabilities for different
items may be a non-monotonic function of the attribute.

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