chapter 4- validity and reliability

8/13/2019 Chapter 4- Validity and Reliability

1/23

VALIDITY AND

RELIABILITYChapter Four


2/23

CHAPTER OBJECTIVES

Define validity and reliability

Understand the purpose for needing valid andreliable measures

Know the most utilized and important types ofvalidityseen in special education assessment

Know the most utilized and important types of

reliabilityseen in special education assessment


3/23

VALIDITY

Denotes the extent to whichan instrument is measuringwhat it is supposed tomeasure.


4/23

Criterion-Related Validity

A method for assessing thevalidity of an instrument by

comparing its scores with anothercriterion known already to be ameasure of the same trait or skill.


5/23

validity coefficient

Criterion-related validity is usually

expressed as a correlation between

the test in question and the

criterion measure. The correlation

coefficient is referred to as a


6/23


7/23

PREDICTIVE VALIDITY

The extent to which a

procedure allowsaccurate predictions

about a subjectsfuturebehavior


8/23

CONTENT VALIDITY

Whether the individual

items of a testrepresent what you

actually want toassess


9/23

CONSTRUCT VALIDITY

The extent to which a test measures atheoretical construct or attribute.

CONSTRUCTAbstract concepts such as intelligence,

self-concept, motivation, aggression andcreativity that can be observed by some

type of instrument.


10/23

A tests constructvalidity is often

assessed by itsconvergentand

discriminantvalidity.


11/23

FACTORS AFFECTING VALIDITY

1. Test-related factors

2. The criterion to which you

compare your instrument maynot be well enough established

3. Intervening events4. Reliability


12/23

RELIABILITY

The consistency of measurements

A RELIABLE TESTProduces similar scores across various

conditions and situations, including

different evaluators and testingenvironments.


13/23

How do we account for an individualwho does not get exactly the sametest score every time he or she takes

the test?

1. Test-takers temporary psychological orphysical state

2. Environmental factors

3. Test form4. Multiple raters


14/23

RELIABILITY COEFFICIENTS

The statistic for expressingreliability.

Expresses the degree ofconsistency in the measurementof test scores.

Donoted by the letter r with twoidentical subscripts (rxx)


15/23

TEST-RETEST RELIABILITY

Suggests that subjects

tend to obtain the samescore when tested at

different times.


16/23

Split-Half Reliability

Sometimes referred to asinternal consistency

Indicates that subjects scoreson some trials consistently

match their scores on othertrials


17/23

INTERRATER RELIABILITY

Involves having two raters independentlyobserve and record specified behaviors,

such as hitting, crying, yelling, and getting

out of the seat, during the same time period

TARGET BEHAVIOR

A specific behavior the observer islooking to record


18/23

ALTERNATE FORMS RELIABILITY

Also known as equivalent forms reliabilityor parallel forms reliability

Obtained by administering two equivalent

tests to the same group of examinees Items are matched for difficulty on each

test

It is necessary that the time framebetween giving the two forms be as shortas possible


19/23

STANDARD ERROR ofMEASUREMENT (SEM)

Gives the margin or error that you should

expect in an individual test score because of

imperfect reliability of the test

OBTAINED SCOREThe score you get when you administer a test

Consists of two parts: the true scoreand theerror score


20/23

Evaluating the Reliability Coefficients

The test manual should indicate why acertain type of reliability coefficient wasreported.

The manual should indicate the conditionsunder which the data were obtained

The manual should indicate the importantcharacteristics of the group used ingathering reliability information


21/23

FACTORS AFFECTING RELIABILITY

1. Test length

2. Test-retest interval

3. Variability of scores

4. Guessing

5. Variation within the test situation


22/23

CHAPTER OBJECTIVES

Define validity and reliability

Understand the purpose for needing valid andreliable measures

Know the most utilized and important types ofvalidityseen in special education assessment

Know the most utilized and important types of

reliabilityseen in special education assessment


23/23

THE END

chapter 4- validity and reliability

Documents