Validity and reliability.pptx

8/14/2019 Validity and reliability.pptx

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VALIDITYANDRELIABILITYAyaz Muhammad Khan


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CONTENT

Importance of valid instrument

What is validity?

Types of validity evidence

What is reliability? Difference between validity

Types of reliability

Measurement error


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IMPORTANCEOFVALIDINSTRUMENT

Quality of instrument use in research is very

important and to ensure the data that researcher

collect is valid and reliable or not.

Validity is the extent to which to a test measures

what we actually wish to measure.

Reliability has to do with the accuracy and precision

of a measurement procedure.

Practicality is concerned with a range of factors of

economy convenience and interpretability The

characteristics of good measurement


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VALIDITY

Defined as referring to the appropriateness,

correctness, meaningfulness, and usefulness of

specific inference researcher make based on data

they collect.

Validation is the process of collecting and analyzing

evidence to support such inference.
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TYPESOFVALIDITYEVIDENCE

Content-related evidence of validity=

refer to the content and format of the

instrument. It must be consistent with definition of

variable and sample of subject to measured.

Criterion related evidence of validity=

refer to the relationship between scores

obtained using the instrument and scores obtained

using one or more other instrument.

Construct-related evidence of validity=

refer to the nature of the psychological

construct or characteristic being measured by

instrument.


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TYPESOFVALIDITY

Face validity: Face validity simply means the

validity at face value. As a check on face

validity, test/survey items are sent to teachers

to obtain suggestions for modification. Because

of its vagueness and subjectivity,psychometricians have abandoned this concept

for a long time.


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CONTENTVALIDITY

Checking to make sure that you have picked

questions that cover the areas you want to cover,

thoroughly and well.

Difficulties: important to ensure that all major aspect

that cover by test item and in the correct proportion.


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CONSTRUCTVALIDITY

Construct validitydefines how well a test or

experiment measures up to its claims.

Convergent validity and discriminate validity are

commonly regarded as subsets of construct validity.

Convergent validitytests that constructs that are

expected to be related are, in fact, related.

Discriminate validity(or divergent validity) tests

that constructs that should have no relationship do,

in fact, not have any relationship.
http://www.experiment-resources.com/construct-validity.htmlhttp://www.experiment-resources.com/construct-validity.html


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CRITERIONVALIDITY

Criterion validity assesses whether a test reflects a

certain set of abilities.

Concurrent validitymeasures the test against a

benchmark test and high correlation indicates that

the test has strong criterion validity.

Predictive validityis a measure of how well a test

predicts abilities. It involves testing a group of

subjects for a certain construct and then comparing

them with results obtained at some point in thefuture.
http://www.experiment-resources.com/concurrent-validity.htmlhttp://www.experiment-resources.com/predictive-validity.htmlhttp://www.experiment-resources.com/predictive-validity.htmlhttp://www.experiment-resources.com/concurrent-validity.html


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RELIABILITY

Reliability is the consistency of your measurement,

or the degree to which an instrument measures the

same way each time it is used under the same

condition with the same subjects. In short, it is the

repeatability of your measurement.

Example: A measure is considered reliable if a

person's score on the same test given twice is

similar. It is important to remember that reliability is

not measured, it is estimated.


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VALIDITYVS. RELIABILITY


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Reliable but not

valid Valid and reliable


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TEST-RETEST

Test/retest reliability is evaluated by giving the

same set of questions on two different occasions. If

the results are consistent, then the measure is said

to be reliable.

a class of children are given several tests that are

intended to assess the same abilities. A week and a

month later, they are given the same tests. With

allowances for learning, the variation in the test andretest results are used to assess which tests have

better test-retest reliability.


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EQUIVALENTFORMSMETHOD

When equivalent form method is used, two different

but equivalent forms of an instrument are

administered to the same group of individual during

the same time period.


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INTERNAL-CONSISTENCYMETHODS

The several internal consistency method of

estimating reliability are:

Split half

procedure


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KUDER-RICHARDSONAPPROACH

Most frequently employed method to determined

the internal consistency.

Alpha coefficient: one split-half reliability and then

randomly divide the items into another set of split

halves and recomputed, and keep doing this until

we have computed all possible split half estimates

of reliability. Cronbach's Alpha is mathematically

equivalent to the average of all possible split-half

estimates, although that's not how we compute it. Limitation: not use full for heterogeneous test.


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STANDARDERROROFMEASUREMENT

It shows the index the extend to which a

measurement vary under changed circumstance.

For example it will be smaller if it include only error

due to different content (internal consistency or

equivalent) or passage of time (test retest)

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