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VALIDITY AND RELIABILITY. Chapter Four. CHAPTER OBJECTIVES. Define validity and reliability Understand the purpose for needing valid and reliable measures Know the most utilized and important types of validity seen in special education assessment

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chapter objectives
CHAPTER OBJECTIVES
  • Define validity and reliability
  • Understand the purpose for needing valid and reliable measures
  • Know the most utilized and important types of validity seen in special education assessment
  • Know the most utilized and important types of reliability seen in special education assessment
validity
VALIDITY
  • Denotes the extent to which an instrument is measuring what it is supposed to measure.
criterion related validity
Criterion-Related Validity
  • A method for assessing the validity of an instrument by comparing its scores with another criterion known already to be a measure of the same trait or skill.
validity coefficient
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

concurrent validity
CONCURRENT VALIDITY

The extent to which a

procedure correlates

with the current

behavior of subjects

predictive validity
PREDICTIVE VALIDITY

The extent to which a procedure allows accurate predictions about a subject’s future behavior

content validity
CONTENT VALIDITY

Whether the individual items of a test represent what you actually want to assess

construct validity
CONSTRUCT VALIDITY

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

CONSTRUCT

Abstract concepts such as intelligence, self-concept, motivation, aggression and creativity that can be observed by some type of instrument.

slide10
A test’s construct validity is often assessed by its convergent and discriminantvalidity.
factors affecting validity
FACTORS AFFECTING VALIDITY
  • Test-related factors
  • The criterion to which you compare your instrument may not be well enough established
  • Intervening events
  • Reliability
reliability
RELIABILITY

The consistency of measurements

A RELIABLE TEST

Produces similar scores across various conditions and situations, including different evaluators and testing environments.

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How do we account for an individual who does not get exactly the same test score every time he or she takes the test?
  • Test-taker’s temporary psychological or physical state
  • Environmental factors
  • Test form
  • Multiple raters
reliability coefficients
RELIABILITY COEFFICIENTS
  • The statistic for expressing reliability.
  • Expresses the degree of consistency in the measurement of test scores.
  • Donoted by the letter r with two identical subscripts (rxx)
test retest reliability
TEST-RETEST RELIABILITY

Suggests that subjects tend to obtain the same score when tested at different times.

split half reliability
Split-Half Reliability
  • Sometimes referred to as internal consistency
  • Indicates that subjects’ scores on some trials consistently match their scores on other trials
interrater reliability
INTERRATER RELIABILITY

Involves having two raters independently

observe 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 is looking to record

alternate forms reliability
ALTERNATE FORMS RELIABILITY
  • Also known as equivalent forms reliability or 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 frame between giving the two forms be as short as possible
standard error of measurement sem
STANDARD ERROR of MEASUREMENT (SEM)

OBTAINED SCORE

  • The score you get when you administer a test
  • Consists of two parts: the true score and the error score

Gives the margin or error that you should

expect in an individual test score because of

imperfect reliability of the test

evaluating the reliability coefficients
Evaluating the Reliability Coefficients
  • The test manual should indicate why a certain type of reliability coefficient was reported.
  • The manual should indicate the conditions under which the data were obtained
  • The manual should indicate the important characteristics of the group used in gathering reliability information
factors affecting reliability
FACTORS AFFECTING RELIABILITY
  • Test length
  • Test-retest interval
  • Variability of scores
  • Guessing
  • Variation within the test situation
chapter objectives22
CHAPTER OBJECTIVES
  • Define validity and reliability
  • Understand the purpose for needing valid and reliable measures
  • Know the most utilized and important types of validity seen in special education assessment
  • Know the most utilized and important types of reliability seen in special education assessment