# What is KR21 reliability?

## What is KR21 reliability?

KR-20/KR-20 are measures of test reliability, Kuder-Richardson Formula 20, or KR-20, is a measure reliability for a test with binary variables (i.e. answers that are right or wrong). The KR20 is used for items that have varying difficulty. For example, some items might be very easy, others more challenging.

## How do you calculate the reliability of the KR21 index?

The formula for KR21 for scale score X is K/(K-1) * (1 – U*(K-U)/(K*V)) , where K is the number of items,U is the mean of X and V is the variance of X.

Is KR 21 reliable?

KR-21 tends to be a more conservative estimate of reliability than KR-20, which in turn is a more conservative estimate than Cronbach’s α.

What is reliability coefficient?

A reliability coefficient is a measure of the proportion of true variance relative to the total observed score variance resulting from the application of a measurement protocol (such as a test, a scale, an expert rating, etc.) to a population of individuals.

### What is alternate reliability?

Alternate-form reliability is the consistency of test results between two different – but equivalent – forms of a test. Alternate-form reliability is used when it is necessary to have two forms of the same tests. The resulting coefficient is called the alternate- form coefficient of reliability.

### What are the two types of reliability coefficients?

There are two types of reliability – internal and external reliability. Internal reliability assesses the consistency of results across items within a test. External reliability refers to the extent to which a measure varies from one use to another.

When to use KR20 or kr21 reliability coefficients?

You can use the KR-20, KR-21 and Cronbach Alfa reliability coefficients when all of the following conditions are met: Data should be parallel, equivalent or uniform measurements, not congeneric; The test must be one dimensional, The test should not be speed test.

How to calculate the kr21 formula in Excel?

The Aggregate procedure is used to compute the pieces of the KR21 formula and save them in a new data set, (kr21_info). With that new data set active, a Compute command is then used to calculate the KR21 coefficient.. /SUMMARY=TOTAL MEANS VARIANCE. compute Nitems = nvalid (item1 to item6).

## When to use kurder-Richardson 21 or KR20?

Can some one please tell me when i can use the Kurder-Richardson 21 Formula, KR20 (Coefficient Alpha) or spearman-Brown formula to calculate the reliability coefficient of a test. Sifuna. Join ResearchGate to ask questions, get input, and advance your work.

## Where can I find the kr21 data set?

All of the steps in the KR21 calculation can be performed in the menu system, or graphic user interface (GUI). The Aggregate procedure is available under Data->Aggregate. After running Aggregate, the KR21_info data set will will be listed in the Windows menu of SPSS Statistics and can be activated by clicking that item.