The purpose of this article was to empirically document the magnitudes of alpha coefficients obtained in behavioral research, compare these obtained values with guidelines and recommendations set forth by individuals such as nunnally 1967, 1978, and provide insights. Below, for conceptual purposes, we show the formula for the cronbachs alpha. Metaanalysis of cronbachs coefficient alpha journal of. A framework is provided for a statistically grounded metaanalysis of. This procedure has proved very resistant to the passage of time, even if its limitations are well documented and although there are better options as omega coefficient or the different versions of glb, with obvious advantages especially for applied research in which the items differ in quality. A reliability generalization metaanalysis of coefficient. Peterson despite some limitations, cronbach s coefficient alpha remains the most widely. Distribution of alpha coefficient has been subjected of many studies. However, it may come with some sideeffects because of hidden misconceptions.
First, researchers should report the cronbach s coefficient alpha of hisher own samples to avoid the reliability induction error. The two main families of effect sizes in meta analysis are the standardized mean. The metaanalysis was performed separately for internal consistency, interrater and testretest reliability. The one exception to this was item 4, which would increase the alpha to. Note that, as expected, these values are roughly inversely related to one another citc goes up, alpha if removed goes down. Based on the reliability generalization methodology. Relationship between randomness and coefficient alpha. Accumulate data via metaanalysis, not just results. Oct 31, 2015 internal consistency of the sobda questionnaire was assessed using cronbachs alpha.
Communication research is evolving and changing in a world of online journals, openaccess, and new ways of obtaining data and conducting experiments via the. A metaanalysis of cronbachs coe fficient alpha article pdf available in journal of consumer research 212. There are two suggestions for the use of the bfi44. A comment on the relationship between coefficient alpha and. Petersona metaanalysis of cronbachs coefficient alpha. Cronbach alpha coefficient an overview sciencedirect. Bayesian metaanalysis of cronbachs coefficient alpha to. Testretest two testretest reliability studies over three months exhibited significant correlations of. As such, removal of this item should be considered. Coefficient alpha by cronbach is a measure of internal reliability or consistency of the items in an instrument, index or scale. The metaanalysis of coefficient alpha across many studies is becoming more common in.
The purpose of this article was to empirically document the magnitudes of alpha. Before alpha, researchers were limited to estimating internal consistency of only dichotomously scored items using the kr20 formula. A metaanalysis of four randomized clinical trials to confirm. Spss cronbach s alpha reliability for questionnaires lasu sterg peter akinsola okebukola. Despite some limitations, cronbachs coefficient alpha remains the most widely used. If the deletion of a question causes a considerable increase in alpha then you should consider dropping that question from the questionnaire. This study analyzed the amount of variability in cronbach s coefficient alpha of every dimension in bfi44 and examined predictor variables, including sample size, subjects nationality, test language, average age and gender. A framework is provided for a statistically grounded meta analysis of. Pdf this study is to examine the metaanalysis results acquired from cronbach alpha reliability coefficient being used in hacettepe university journal.
A reliability generalization metaanalysis of coefficient alpha for the maslach burnout inventory. Alpha is reported in nearly every study that involves measuring a construct through multiple test items. A meta analysis of studies reporting the reliability coefficient found that the constructs of perception, values, belief, or behavior tend to report lower alpha values compared to other constructs. Download pdf show page numbers coefficient alpha, or cronbachs alpha, is one way to quantify reliability and represents the proportion of observed score variance that is true score variance. The metaregression analysis revealed that higher alpha coefficients were associated with higher variability of the hrsd total scores. That is, more accurately estimated alpha coefficients get greater weight in the metaanalysis of coefficient alpha. The case of cronbachs coefficient alpha oscar lorenzo olvera astivia, edward kroc, and bruno d. In some of those studies, the sample coefficient alpha in petersons metaanalysis study 1994 on coefficient alpha is obtained from a small sample size n. Despite some limitations, cronbachs coefficient alpha remains the most widely used measure of scale reliability. One consistent result is that coefficient alpha produces an rsquare of approximately. It was found that the coefficient alpha was reported 4286 times, the alpha range was 0. It estimates reliability in the framework of the domain sampling model.
The alpha option in proc corr provides an effective tool for measuring cronbach s alpha, which is a numerical coefficient of reliability. Because intercorrelations among test items are maximized when all items measure the same construct, cronbach s alpha is widely believed to indirectly indicate the. Cronbachs alpha for each measure, cronbachs alpha for a measure if a single item is removed, correlations between an item and the remaining items in the measure called corrected itemscale correlations, the. Making sense of cronbachs alpha pubmed central pmc. Medcalc reports cronbach s alpha with its lower confidence limit feldt, 1965. This practice makes subsequent metaanalysis of mean difference and alpha impossible. A pooled mean for alpha coefficient in random effects model was 0. Robust coefficient alpha and omega with missing and nonnormal data. A reliability generalization meta analysis of coefficient alpha for the maslach burnout inventory denna l. Peterson despite some limitations, cronbach s coefficient alpha remains the most widely used measure of scale reliability. Method, because it is incorrect to say, the test is.
An introduction to computing and interpreting cronbach. Calculating cronbachs alpha coefficient for internal consistency a single statement item was presented to each student and then this same statement was presented to the student 3 weeks later. Cronbachs alpha is a measure used to assess the reliability, or internal consistency, of a set of scale or test items. A metaanalysis of cronbach s coefficient alpha created date. This study is to examine the meta analysis results acquired from cronbach alpha reliability coefficient being used in hacettepe university journal of education. A metaanalysis of cronbach s coefficient alpha, journal of consumer research, volume 21, issue 2, september 1994. Two empirical examples are offered to illustrate these methods, and limitations of reliability generalization are described. Jun 27, 2011 in practice, cronbachs alpha is a lowerbound estimate of reliability because heterogeneous test items would violate the assumptions of the tauequivalent model. The meta analysis of coefficient alpha across many studies is becoming more common in psychology by a methodology labeled reliability generalization. If at all possible, use the standardized alpha coefficient, which is an even more conservative method for calculating reliability. Computation of alpha is based on the reliability of a test relative to other tests with same number of items, and measuring the same construct of interest hatcher, 1994. Pdf questionnaire evaluation with factor analysis and. In a metaanalysis of cronbachs alpha, 4 analyzed 33,000 articles published in different journals between the years 1971 and 1992.
An introduction to computing and interpreting cronbach coefficient alpha in sas chong ho yu, ph. May 26, 2016 the cronbachs alpha is the most widely used method for estimating internal consistency reliability. A meta analysis of cronbach s coefficient alpha created date. Tauequivalent reliability is a singleadministration test score reliability i. This gives rise to a bivariate, binary meta analysis with the withinstudy correlation assumed zero although the betweenstudy correlation is estimated. Measures of stereotyping and prejudice 7 the cronbach alpha coefficient in samples averaged. The purpose of the present study is to investigate if and how external factors could. The metaanalysis of coefficient alpha across many studies is becoming more common in psychology by a methodology labeled reliability generalization. In other words, the reliability of any given measurement refers to the extent to which it is a consistent measure of a concept, and cronbachs alpha is. Coefficient alpha, or cronbach s alpha, is one way to quantify reliability and represents the proportion of observed score variance that is true score variance. Coefficient alpha encyclopedia of research design search form. Research on the use of construct reliability in mis research. The role of item distributions on reliability estimation.
Existing reliability generalization studies have not used the sampling distribution of coefficient alpha for precision weighting and other common meta analytic procedures. The correlation between the 2 administered scales was 0. The average of these values is equivalent to cronbachs alpha. Based on metaanalysis for internal consistency, the pooled cronbach s alpha coefficient from collegeuniversity students with a single department subgroup was 0.
The impact of eliminating scale items on cronbachs alpha. This study is to examine the metaanalysis results acquired from cronbach alpha reliability coefficient being used in hacettepe university journal of education. Results on the standard error of the coefficient alpha index. Uses and abuses of coefficient alpha neal schmitt michigan state university the article addresses some concerns about how coefficient alpha is reported and used. The coefficient alpha is one of the most widely used reliability indices. A reliability metaanalysis for 44 items big five inventory. Cronbachs alpha coefficient is the most popular method of examining reliability. The metaanalysis has an exploratory nature, because no a priori theory concerning the influences of the various potential impacts on r2 exists besides the difference between crosssectional and timeseries data. The criterion for an acceptable cronbach s alpha coefficient is debated in the literature, but to be conservative, any alpha coefficient below.
Cronbachs alpha is regularly adopted in studies in science education. Most items appeared to be worthy of retention, resulting in a decrease in the alpha if deleted. Document resume ed 434 121 author thompson, russel l. A reliability generalization metaanalysis of coefficient alpha for the maslach burnout inventory show all authors. This study disproves the following six common misconceptions about coefficient alpha. An instructors guide to understanding test reliability. Chau1, department of information and systems management, school of business and management, the hong kong university of science and.
Moreover, cronbach concluded that the tests general or dominant factor, in his words, the firstfactor concentration in the test, was the main influence on alpha, and that group factors only affecting responses to subsets of. The use of cronbachs alpha when developing and reporting. Technically speaking, cronbachs alpha is not a statistical test it is a coefficient of reliability or consistency. Psychometric properties of the internet addiction test. Pdf despite some limitations, cronbachs coefficient alpha remains the most widely used measure of scale reliability. The purpose of this study was to synthesize internal consistency cronbach s alpha and testretest reliability for the ams scale and its three subscales. Reliability of the hamilton rating scale for depression. The cronbach s alpha is the most widely used method for estimating internal consistency reliability. Jan 27, 20 using spss to calculate cronbach s alpha reliability of questionnaires lasusterg. Cronbach s 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. Using the inverse of the variance of alpha as a weighting mechanism gives greater weight to alpha coefficients that have smaller variances for the reliability of scores in each sample. This paper proposes a new method to evaluate informative hypotheses for metaanalysis of cronbach s coefficient alpha using a bayesian approach.
This paper proposes a new method to evaluate informative hypotheses for meta. To clarify these misconceptions, this paper will illustrate the computation of cronbach coefficient alpha in a stepbystep manner, and also explain the meaning of each component of the sas output. Reliability is a property of a test that is derived from true. Measures of stereotyping and prejudice final version. In practice, cronbachs alpha is a lowerbound estimate of reliability because heterogeneous test items would violate the assumptions of the tauequivalent model. Cronbachs alpha can be written as a function of the number of test items and the average intercorrelation among the items. A metaanalysis of cronbachs coe fficient alpha robert a. Luckily, alpha is offered in many conventional software packages and is very easy to calculate. Zumbo educational and psychological measurement 0 10. Cronbach university of illinois a general formula a of which a special case is the kuder richardson coefficient of equivalence is shown to be the mean of all splithalf coefficients resulting from. Metaanalysis of coefficient alpha semantic scholar. It is most commonly used when the questionnaire is developed using multiple likert scale statements and therefore to determine if the scale is reliable or not.
It is typically used when the researcher has several likerttype items that are summed or averaged to make a composite score. The valid responses from 2003 phns in the first survey were analyzed for major factors by varimax rotation. The impact of research designs on r2 in linear regression. Frontiers best alternatives to cronbachs alpha reliability. This practice makes subsequent metaanalysis of mean difference and. To understand this statement one must understand the distinction between alpha as defined by cronbach and standardized item alpha.
A reliability generalization study 27 december 2017 journal of management studies, vol. Using and interpreting cronbachs alpha university of. The analysis resulted in five orientation factors and 19 items being selected. Meta analysis of studies of diagnostic tests a special case of multivariate meta analysis is the case of summarising studies of diagnostic tests. This coefficient is a measure of the squared correlation between observed scores and true scores, reliability being thus measured in terms of the ratio of the true.
Cronbach alpha is a reliability test conducted within spss in order to measure the internal consistency i. Reliability is usually expressed numerically as a correlation coefficient, with 0. The formula for cronbach s alpha is n2 x mcov sum varcov 1 where n2 is the square of the number of items in the scale, afcov is the mean interitem covariance, and sum var. These studies have improved our understanding of the scale development process and the behavior of coefficient alpha. In this paper, we study the effect of the elimination of items from a scale so that only those items that correlate highly are chosen. Barnes educational and psychological measurement 2011 71. The confirmatory factor analysis shows a suitable fit to the unifactorial model proposed for the original version of the scale. Cronbachs alpha is a statistic commonly quoted by authors to demonstrate that tests and scales that have been constructed or adopted for research projects are fit for purpose. In this paper, we study the effect of the elimination of items from a scale so that only those. Further details we get the citc value for each item as well as the cronbachs alpha if item is deleted. Cronbachs alpha showed the questionnaire to reach acceptable reliability.
Reliability, cronbachs alpha sage research methods. It estimates testscore reliability from a single test administration using information from the relationship among test items. Type of reliability coefficient one property of alpha cronbach, 1951 is it is one type of internal consistency coefficient. Internal consistency reliability for this study was measured in a variety of ways. Despite some limitations, cronbach s coefficient alpha remains the most widely used measure of scale reliability. In a metaanalysis of cronbachs alpha, 4 analyzed 33,000 articles published in different journals between. Introduction when a person is tested or observed multiple times, such as a student tested for mathematics achievement or a navy machinist mate observed while operating engine room. Next, medcalc calculates the alpha obtained with each question in turn dropped. That is, more accurately estimated alpha coefficients get greater weight in the meta analysis of coefficient alpha. To date, three major articles have analyzed the use of coefficient alpha on scales published in the marketing literature. Spss cronbachs alpha reliability for questionnaires lasu sterg.
The general view on this subject is that the sample coefficient alpha obtained from larger samples tends to produce a more accurate estimate of the population coefficient alpha. A meta analysis is performed by defining an effect size measure that represents an overall numerical result from each study. Existing reliability generalization studies have not used the sampling distribution of coefficient alpha for precision weighting and other common metaanalytic procedures. Metaanalysis of coefficient alpha for scores on the. Reliability coefficient for internal consistency there are several statistical indexes that may be used to measure the amount of internal consistency for an exam. Using a simulation, we estimate the impact on cronbach s alpha as a function of the total number of items in a scale, the number of items chosen, the true correlation among the items, and the sample size. Recently peterson 1994 published a comparable but more extensive metaanalysis concerning cronbachs coefficient alpha. It also shows thai alpha is not a measure of homogeneity or unidimensionality. The metaanalysis of coefficient alpha across many studies is becoming more common in psychology by a. This paper proposes a new method to evaluate informative hypotheses for meta analysis of cronbach s coefficient alpha using a bayesian approach. Cronbach s alpha and mcdonalds omega are widely used reliability or internal consistency measures in social, behavioral and education sciences. The purpose of this article was to empirically document the magnitudes of alpha coefficients obtained in behavioral research. A testretest reliability coefficient was calculated on this individual statement item since individual items can not have a cronbachs alpha. The purpose of the present study is to investigate if and how external factors could influence a largely used.