Relationship Between Validity And Reliability

Relation Between Validity And Reliability Of A Test

Validity And Reliability Are Closely Related. A Test Cannot Be Considered Valid Unless The Measurements Resulting From It Are Reliable.

Likewise, Results From A Test Can Be Reliable And Not Necessarily Valid. Test Validity Is Requisite To Test Reliability. If A Test Is Not Valid, Then Reliability Is Moot.

In Other Words, If A Test Is Not Valid There Is No Point In Discussing Reliability Because Test Validity Is Required Before Reliability Can Be Considered In Any Meaningful Way.

Likewise, If As Test Is Not Reliable It Is Also Not Valid. Therefore, The Two Studies Do Not Examine Reliability.

At The Same Time, The Evaluation Results Cannot Be Perfectly Consistent. There Are Many Factors That Influence The Results.

If A Single Test Is Administered To The Same Group Twice In A Close Succession, Some Variations In The Scores Can Be Expected Because Of Temporary Fluctuations In

• Memory,
• Attention,
• Effort,
• Fatigue And
• Guessing Etc.

Variation In Scores Can Occur Due To Intervening Learning Experiences If Long Time Gap Exists Between Two Tests. Such Extraneous Factors Introduce Certain Amount Of Measurement Error In All Types Of Evaluation.

The Method Of Determining Reliability Is, In Fact, The Means Of Determining The Measurement Error Under Different Conditions.

Methods Of Estimating Reliability Involve Comparing At Least Two Applications Of The Same Instruments Or Equivalent Instruments And Determining The Extent To Which They Agree. The Closer The Agreement, The Greater Is The Reliability.