validity vs reability

8/3/2019 Validity vs Reability

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VALIDITY &RELIABILIT

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Validity


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o (Dictionary):

The state of quality of being valid: to questionthe validity of the argument

Extent to which a test measures what it claims tomeasure. It is vital for a test to be valid in order forthe result to be accurately applied and interpreted.

In terms of assessment:

validity refers to the extent to which a test'scontent is representative of the actual skills

learned and whether the test can allow accurateconclusions concernin achievement.


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Category of validity

i. Content/face validity

ii. Validity related to the criteria

iii. Validity of constructs


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It does not assess memory, when it is supposed tobe assessing problem-solving (and vice versa).

It does not grade someone on the quality of theirwriting, when writing skills are not relevant to thetopic being assessed, but it does when they are.


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Content validity

Does the content of the test measure statedobjectives?

Important validity for teachers to prepare examquestions and the contents in the examsincorporated with the contents, syllabus,curriculum specification and the objectives

The contents depends on the studentsachievement, difficulties, and suitable testeditems.

Example: final year exams that only focus oncertain topics but ignore other topics thus it

invalid.


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Validity related to thecriteriaRelate the validity to the stated criteria.

2 types:Predictive validity

predict the future performance

Concurrent validity

the new exams are identical to thepast exams. Accuracy to identify the

current based on status regarding


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Validity of constructs

Constructs, such as creativity, honesty,and intelligence, are concepts used by

social scientists to help explain empiricaldata about a phenomenon or toconstruct a theory

Construct validity measures the extent to

which an examination actually measureswhat the specification says it is intendedto measure.


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languages examinations are intended to measure

candidates' skills in understanding, speaking,reading and writing the foreign language.

If a specification requires candidates to acquirepractical skills, the assessment should include apractical assessment and should not just requirecandidates to, for example, write about how theywould carry out a practical activity.


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Reliability


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What is reliability ?used in experiment, test or any

measuring procedure. that will show the

same result when we repeat. Without anycondition of the independent observersthat able to repeat the researchprocedure.

In research, the term reliability means"repeatability" or "consistency". Ameasure is considered reliable if it would

give us the same result over and over


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How to determine the

reliability of instrumentsthroughTest-retest methodTest is repeated on the same subjects at a future date.

Results are compared with initial test to determine stability.

Equivalent form

Determine by relating two sets of test scores to one anotherto highlight the degree of relationship.

Inter-rater Reliability

Dependent upon the ability of two or more individuals to beconsistent. For example, when two or more teachers use arating scale with which they are rating the students oral

responses in an interview (1 being most negative, 5 beingmost positive). If a teacher gives a 1 to a student, while


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Internal Consistency

Assess the same characteristics, skill orquality.

Helps teachers interpret data and predict

the value of scores and the limits ofrelationship among students.

Split Half Method

The Spearman-Brown prophecy formula isapplied to the correlation to determine thereliability.

Methods that helps teachers to determine


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Factor affecting reliability

Test length.

the longer a test is, the more reliable it is.

Speed.

When a test is a speed test, reliability can be problematic. It isinappropriate to estimate reliability using internal consistency,test-retest, or alternate form methods.

This is because not every student is able to complete all of theitems in a speed test. In contrast, a power test is a test in whichevery student is able to complete all the items.

Item difficulty

When there is little variability among test scores, the reliabilitywill be low. Thus, reliability will be low if a test is so easy thatevery student gets most or all of the items correct or so difficultthat every student gets most or all of the items wrong.


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Objectivity

Objectively scored tests, rather than subjectivelyscored tests, show a higher reliability

Variation with the testing situation

Difficulties in the testing situation. For example,students misunderstanding or misreading testinstructions, noise level, distractions, and sicknesscan cause test scores to vary.


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Relationship between

validity & reliabilityValidity and reliability are closely related.

A test cannot be considered valid unlessthe measurements resulting from it arereliable


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Likewise, results from a test can bereliable and not necessarily valid.

validity vs reability

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