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.

What is KR-20 reliability coefficient?

The KR20 formula is a measure of internal consistency for examinations with dichotomous choices. It produces a correlation measure between 0 where a high KR20 coefficient (e.g., >0.90) is indicative of a homogeneous test. Usually, a KR20 figure of 0.8 is considered the minimal acceptable value.

How do you interpret Kuder-Richardson reliability coefficient?

KR-20 scores range from 0-1 (although it is possible to obtain a negative score); 0 indicates no reliability and 1 represents perfect test reliability. A KR-20 score above 0.70 is generally considered to represent a reasonable level of internal consistency reliability.

What is reliability coefficient?

Definition of reliability coefficient : a measure of the accuracy of a test or measuring instrument obtained by measuring the same individuals twice and computing the correlation of the two sets of measures.

How do you calculate variance in Kuder-Richardson reliability coefficient?

σ2 = variance of the total scores of all the people taking the test = VARP(R1) where R1 = array containing the total scores of all the people taking the test. Values range from 0 to 1.

What is the difference between KR-20 and KR-21?

KR-21 is a simplified version of KR-20, which can be used when the difficulty of all items on the test are known to be equal. Like KR-20, KR-21 was first set forth as the twenty-first formula discussed in Kuder and Richardson’s 1937 paper. Similarly to KR-20, K is equal to the number of items.

What is considered a good reliability coefficient?

The following guidelines can be used: 0.9 and greater: excellent reliability. Between 0.9 and 0.8: good reliability. Between 0.8 and 0.7: acceptable reliability.

Which Kuder Richardson formula is used to estimate?

In psychometrics, the Kuder–Richardson formulas, first published in 1937, are a measure of internal consistency reliability for measures with dichotomous choices. They were developed by Kuder and Richardson.

How do you calculate variance in Kuder Richardson reliability coefficient?

What does a reliability coefficient of 0.80 mean?

As a general rule, a reliability of 0.80 or higher is desirable for instructor-made tests. The higher the reliability estimated for the test, the more confident one may feel that the discriminations between students scoring at different score levels on the test are, in fact, stable differences.

What is a reliability coefficient?

What does .90 reliability coefficient mean?

90 on a test means that 90% of the test score is accurate while the remaining 10% consists of standard error. If the r=0.6, it means that only 60% of the test score is reliable and the other 40% may be caused by an error. Thus, the higher the reliability coefficient is, the lower the standard error is.

What is Kuder Richardson KR-20 & KR 21 formulas?

The Kuder-Richarson Formula 20, often abbreviated as KR-20, and the Kuder-Richardson Formula 21, abbreviated KR-21, are measures of internal consistency for measures that feature dichotomous items.

Is 0.5 Cronbach alpha reliable?

Alpha’s coefficients of 0.5 are considered unsatisfactory. Most of the guidelines recommend 0.6 or higher accepted. It is dependable of your test. For a high-stakes test, the suggested alpha is higher than 0.8.

What is Kuder-Richardson KR-20 & KR-21 formulas?

What is a good reliability coefficient?

Between 0.9 and 0.8: good reliability. Between 0.8 and 0.7: acceptable reliability. Between 0.7 and 0.6: questionable reliability. Between 0.6 and 0.5: poor reliability.

What is the difference between Kuder Richardson 20 and 21?

What does a 0.4 Cronbach’s alpha mean?

Cronbach alpha is applied to determine how reliable your items in questionnaire. If the cronbach alpha below than 0.50, it indicates that your items are inappropriate. According to Nunnally (1978), the cronbach alpha should be greater than 0.7. Cite.

Is 0.7 A good reliability?

A general accepted rule is that α of 0.6-0.7 indicates an acceptable level of reliability, and 0.8 or greater a very good level. However, values higher than 0.95 are not necessarily good, since they might be an indication of redundance (Hulin, Netemeyer, and Cudeck, 2001).

When to use KR-20 and KR-21 reliability coefficient?

Thanks. 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.

Can SPSS calculate the Kuder-Richardson 20 and kr21 coefficients of reliability?

Can SPSS calculate the Kuder-Richardson 20 (KR20) and KR21 coefficients of reliability for a scale? The KR20 is a special case of Cronbach’s Alpha in which the items are binary variables (usually scored as 0 or 1). The RELIABILITY procedure can calculate Alpha and therefore can calculate KR20 for binary item variables.

What is the difference between aggregate and kr21?

The KR21 formula uses the population (“biased”) estimate of the scale score variance, whereas Aggregate computes the sample (“unbiased”) estimate. Also, Aggregate will save the standard deviation of a variable to the new data set, but does not have a function to save the variance.

How to calculate kr21_scorea in Excel?

compute kr21_ScoreA = k/ (k – 1) * (1 – (scoreA_mean* (k – scoreA_mean)/ (k*scoreA_sd**2* (N_ScoreA -1)/N_ScoreA))). list. Here are a few explanatory notes for the commands.