Validity and Reliabilty of Scales

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VALIDITY &RELIABILITY OF SCALES
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Validity:Validity refers to the extentto which a test measureswhat we actually wish tomeasure

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Test of Validity

Validity is the most critical criterionand indicates the degree to which aninstrument measures what it is supposedto measure. Validity can also be thought of asutility. validity is the extent to whichdifferences found with a measuringinstrument reflect true differences amongthose being tested.


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Three Types Of Validity

(i)Content validity(ii)Criterion-related validity

(iii) Construct validity.


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It is the extent to which a measuringinstrument provides adequate coverage of thetopic under study. Its determination is primarily judgmentaland intuitive. It can also be determined by using a panelof persons who shall judge how well themeasuring instrument meets the standards. There is no numerical way to express it.

Content validity :
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It relates to our ability to predictsome outcome or estimate theexistence of some current condition. This form of validity reflects thesuccess of measures used for someempirical estimating purpose.

Criterion-related validity


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The concerned criterion must possess the followingqualities:Relevance: (A criterion is relevant if it isdefined in terms we judge to be the proper measure.)Freedom from bias: (Freedom from bias isattained when the criterion gives each subjectan equal opportunity to score well.)Reliability:(A reliable criterion is stable orreproducible.)Availability: (The information specified by thecriterion must be available.)


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It is the most complex and abstract.

A measure is said to possess construct validity to

the degree that it confirms to predictedcorrelations with other theoretical propositions.

Construct validity is the degree to which scores

on a test can be accounted for by the explanatory

constructs of a sound theory.

CONSTRUCT VALIDITY


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RELIABILTY:Reliability has to do with theaccuracy and precision of ameasurement procedureValidity and Reliability are usedfor the sound measurement

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The test of reliability is another important testof sound measurement.A measuring instrument is reliable if it providesconsistent results.Reliable measuring instrument does contributeto validity,but a reliable instrument need not be a validinstrument.

Test of Reliability


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Two Aspects of ReliabilityStability

Equivalence

The stability aspect is concerned with securingconsistent results with repeated measurementsof the same person and with the sameinstrument.

The equivalence aspect considers howmuch error may get introduced bydifferent investigators or different samplesof the items being studied.


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Reliability can be improved by two ways:

(I) By standardizing: the conditions under which

the measurement takes place i.e., we must

ensure that external sources of variation such

as boredom, fatigue, etc., are minimized to the

extent possible. That will improve stabilityaspect.


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(ii) By carefully designed directions: formeasurement with no variation from groupto group, by using trained and motivatedpersons to conduct the research and also bybroadening the sample of items used. Thiswill improve equivalence aspect.


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Validity and Reliabilty of Scales

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