# HRS 610 Lecture Notes - Lecture 7: Inter-Rater Reliability, Confidence Interval, Projective TestPremium

9 pages36 viewsFall 2016

Department

HRS - HRS-Human Rehab ServicesCourse Code

HRS 610Professor

BezyakLecture

7This

**preview**shows pages 1-3. to view the full**9 pages of the document.**1. Reliability

Reliability

oThe degree to which tests scores are consistent over repeated

applications of a measurement procedure and hence are

inferred to be dependable and repeatable.

oFrom the perspective of classical test theory, an examinee's

obtained test score (X) is composed of two components: a true

score component (T) and an error component (E):

X=T+E

oThe true score component reflects the examinee's status with

regard to the attribute that is measured by the test if tested

under perfect conditions.

oThe error component represents measurement error because

life is not perfect.

oMeasurement error is random error. It is due to factors that are

irrelevant to what is being measured by the test and have an

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unpredictable (unsystematic) effect on an examinee's test score.

Measurement error is assumed to be randomly distributed.

oThe score you obtain on a test is likely due to the knowledge you

have about the topics addressed by exam items (T) and the

effects of random factors (E). Random factors include the way

test items are written and any alterations in anxiety, attention,

or motivation you experience while taking the test.

oWhenever we administer a test to examinees, we would like to

know how much of the scores reflects "truth" and how much

reflects error.

oIt is a measure of reliability that provides an estimate of the

proportion of true score that is present in the person’s actual

score.

oWhen a test is reliable it provides dependable, consistent

results, and for this reason the term consistency is often given as

a synonym for reliability

Reliability Coefficient

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oMost methods for estimating reliability produce a reliability

coefficient, which is a correlation coefficient that ranges in value

from 0.0 to + 1.0.

oWhen a test's reliability coefficient is 0.0, all variability in

obtained test scores is due to measurement error.

oConversely, when a test's reliability coefficient is + 1.0, all

variability in scores reflects true score variability.

oThe reliability coefficient is symbolized with the letter r.

oRegardless of the method used to calculate a reliability

coefficient, the coefficient is interpreted directly as the

proportion of variability in obtained test scores that reflects true

score variability.

For example, a reliability coefficient of .84 indicates that

84% of variability in scores is due to true score differences

among examinees, while the remaining 16% (1.00 - .84) is

due to measurement error.

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