Evidence-Based Practice for Nurses

Type

What Is

Determined? Description

Test-retest Stability New instrument is given at

two different times under the

same conditions. Scores are

correlated. Strong positive

correlations indicate good

reliability.

Parallel or

alternate

Stability

Equivalence

New instrument is given in

two different versions. Scores

are correlated. Strong positive

correlations indicate good

reliability.

Interrater

reliability

Equivalence Two observers measure

the same event. Scores are

correlated. Strong positive

correlations indicate good

reliability.

Split-half Internal

consistency

The items are divided to

form two instruments. Both

instruments are given and

the halves are compared

using the Spearman-Brown

formula.

Item to total Internal

consistency

Each item is correlated to the

total score. Reliable items

have strong correlations with

the total score.

Kuder-

Richardson

coefficient

Internal

consistency

Used with dichotomous

items. A computer is used to

simultaneously compare all

items.

Cronbach’s

alpha

Internal

consistency

Used with interval or ratio

items. A computer is used to

simultaneously compare all

items.

TABLE 10-3

Reliability: Does the Instrument

Yield the Same Results on Repeated

Measurements?

KEY TERMS

internal

consistency:

An attribute of

reliability when

all items on

an instrument

measure the same

concept

test-retest

reliability: A test

for instrument

reliability when

new instruments

are given at two

different times

under the same

conditions; scores

are correlated, and

strong positive

correlations indicate

good reliability

parallel form: A

test for instrument

reliability in which

two different

versions of new

instruments are

given. Scores are

correlated, and

strong positive

correlations indicate

good reliability; also

known as alternate

form

alternate form: A

test for instrument

reliability in which

two different

versions of new

instruments are

given. Scores are

correlated, and

strong positive

correlations indicate

good reliability; also

known as parallel

form

10.3 Validity and Reliability 269