Excel spreadsheet to calculate instrument reliability. Penjelasan uji reliabilitas instrumen lengkap uji statistik. For the love of physics walter lewin may 16, 2011 duration. Using a structural equation modeling framework for estimating composite reliability of congeneric measures raykov, 1997, the approach takes repeated samples from a given sample and then estimates. To investigate the effect of violating the assumption of equal item difficulty on kuderrichardson kr formula 21 reliability coefficient, 670 eighthand ninth grade students were administered 26 short, homogeneous tests of mathematics concepts and skills. Lesson 4 analysis of test results linkedin slideshare. A correct question scores 1 and an incorrect question scores 0. The kuderrichardson coefficient showed good internal consistency. Kudarrichardson 20 is run the exact same way as cronbachs alpha in spss and interpreted the same way as well. Can some one please tell me when i can use the kurderrichardson 21 formula, kr20 coefficient alpha or spearmanbrown formula to calculate the reliability coefficient of a test. Reliability, kuderrichardson formulapage 1418 sage. In addition, kr20 computes the item difficulty proportion of right answers, the average value of item difficulty, the item variance, the itemtest pointbiserial correlation coefficients, and the average value of itemtest correlation coefficients. A method for obtaining standard errors and confidence intervals of composite reliability coefficients based on the bootstrap method is proposed. Item analysis technique to improve test items and instruction 2.
Although it can be applied to any test item responses that are dichotomously scored, it is most often used in classical psychometric analysis of psychoeducational tests and, as such. The aim of this study is to adapt the survey of pedagogical content knowledge in early childhood mathematics, developed by smith 1998, to turkish. The kuder and richardson formula 20 test checks the internal consistency of measurements with dichotomous choices. Both kr formula 20 and kr formula 21 were used to estimate reliability on each test. Computes the reliability coefficient of a set of dichotomous items, whereas cronbachs alpha is used for multipoint scales. I use the kr20 instead of the cronbachs alpha because my items are noted on a binary scale. The analysis of the roc curve established an area under the curve of 86. Results obtained by the kudarrichardson formula 20 adapted for use with rkw scoring are compared with three other reliability formulas. Dear all, i am checking how to do a kuderrichardson reliability coefficients kr20 in spss. Simply select your manager software from the list below and click on download. Kudarrichardson 20 cannot be used for response sets that have three or more levels. The characteristics of the patients have been presented in table 1. Assessment of psychometric properties of the brazilian.
Both the interrater reliability for averaged ratings and the intraclass correlation for a single, typical judge are derived from the repeatedmeasures anova output in the reliability program. Essentially it lets you know whether the exam as a whole discriminated among students who mastered the subject matter and those who did not. Differences between kuderrichardson formula 20 and. It is a general version because the kuderrichardson coefficient applies only to dichotomous items, whereas alpha applies to any set of items regardless of the response scale cortina, 1993. These complement the standard excel capabilities and make it easier for you to perform the statistical analyses described in the rest of this website. The kr21 could be calculated in spss by using the aggregate procedure to save kr21 formula components to an active file, where they could be input into a compute command to calculate kr21. The kudarrichardson 20 kr20 formula generates a raw reliability coefficient for survey items that use these response sets. Cronbachs alpha will generally increase as the intercorrelations among test items increase, and is thus known as an internal consistency estimate of reliability of test scores.
An approximation to the sampling distribution of kuderrichardson reliability formula 20 is derived, using its algebraic equivalent obtained through an itemsbysubjects analysis of variance. Kuderrichardson 20 kr20 scale reliability calculation. There are two ways in which sumscale combines the scores of a set of ordinal variablesitems. Kuderrichardson 20 kr20 scale reliability calculation can spss calculate the kr20 reliability figure for assessing scales that are composed of dichotomous items. Statistics that are reported by default include the number of cases, the number of items, and reliability estimates as follows.
Kuderrichardson reliability coefficients kr20 and kr21. The name of this formula stems from the fact that is the twentieth formula discussed in kuder and richardsons seminal paper on test reliability. I want to use the kr20 to learn about the internal consistency of items. Splithalf reliability analysis spearmanbrown coefficient. Item analysis with spss software linkedin slideshare. Kuder and richardson 1937 special cases of cronbachs more general equation for parallel tests. Simple procedures for estimating interrater reliability are presented using the new spss for windows 5. The theoretical distribution is compared to empirical estimates of the sampling distribution to assess how crucial certain assumptions are. With kr20 formula giving a better estimate for reliability of the test concerned than when the kr21 formula is invoked. Assessment of the accuracy of a new tool for the screening.
Validity is defined as the extent to which a concept is accurately measured in a quantitative study. The second measure of quality in a quantitative study is reliability, or the accuracy of an instrument. Splithalf reliability and the spearmanbrown coefficient using spss duration. For more information about reading data in spss, see the spss command syntax reference. The analysis of the instruments internal consistency revealed a kuderrichardson coefficient of 0. Robust coefficients alpha and omega and confidence.
For more information about intraclass coefficients as a measure of reliability, see spss library. Alpha is a general version of the kuderrichardson coefficient of equivalence. T o resolve this i ssue, kuder and richardson 1937 proposed a reliability formula called kr 20 that can be used for data on dichotomously scored items e. Cronbachs alpha continuous and dichotomous data in spss.
It is equivalent to performing the split half methodology on all combinations of questions and is applicable when each question is either right or wrong. The theoretical range of the coefficient of determination is. Because intercorrelations among test items are maximized when all items measure the same construct, cronbachs alpha is widely believed to indirectly indicate the degree to which a set of items. Online statistics helps you in estimating the test reliability using kuderrichardson formula 21 calculator. Using and interpreting cronbachs alpha university of. For more information on cronbachs alpha, see spss library. The kr20, or kuderrichardson formula, measures overall test reliability. Hi everybody, i need to calculate internal consistency reliability, using kuderrichardson formula 20 i was wondering if someone can explain how to calculate it using spss 20. Alpha should be calculated whenever possible, but kr21 can provide reasonable reliability estimates for tests with dichotomous items. The above syntax will provide the average interitem covariance, the number of items in the scale, and the \ \alpha \ coefficient. Kuder and richardson formula 20 real statistics using excel.
The reliability estimates are incorrect if you have missing data. Kuderrichardson reliability coefficients kr20 in spss. Pada bahasan kali ini kita tidak membahas lebih lanjut tentang rumus kr ini, karena akan dijelaskan pada postingan artikel berikutnya. The approximate sampling distribution of kuderrichardson.
You can select various statistics that describe your scale and items. The kr reliability coefficient can be thought of as the average correlation obtained from all possible split halves reliability estimates. I have created an excel spreadsheet to automatically calculate splithalf reliability with spearmanbrown adjustment, kr20, kr21, and cronbachs alpha. Eric ed074095 an assessment of the kuderrichardson. In psychometrics, the kuderrichardson formula 20 kr20, first published in 1937, is a measure of internal consistency reliability for measures with dichotomous choices. For example, a survey designed to explore depression but which actually measures anxiety would not be considered valid. The final analysis included 201 participants under treatment with warfarin. After the translation stage of the turkish form, it was applied to. Also reported are item whole correlations, alpha if an item is omitted, and item means and. Untuk perhitungan koefisien reliabilitas dapat dilakukan dengan menggunakan rumus kuderrichardson kr20 dan kuderrichardson kr21. Cronbachs coefficient alpha is a widely used reliability measure in social, behavioral, and education sciences.
How to use spss kuderrichardson20 kr20 reliability analysis. Krl20 and kr21 only work when data are entered as 0 and 1. A statistic that provides an indication of the degree to which two sets of scores are related. Click on an icon below for a free download of either of the following files. Based on parallel tests administered at the same sitting the kr 20 estimates are compared with alternateform correlations and with oddeven correlations adjusted by the spearmanbrown prophecy formula. What is the difference between kuderrichardson kr20 and. Download pdf show page numbers the kuderricharson formula 20, often abbreviated as kr20, and the kuderrichardson formula 21, abbreviated kr21, are measures of internal consistency for measures that feature dichotomous items.