Med J Islam Repub Iran. This project has received funding from the, You are free to copy, share and adapt any text in the article, as long as you give, Select from one of the other courses available, Creative Commons-License Attribution 4.0 International (CC BY 4.0), European Union's Horizon 2020 research and innovation programme. Examples: Reporting exact and approximate figures. Quick start Cronbach's alpha and the average interitem covariance of 6 variables alpha v1 v2 v3 v4 v5 v6 A Review on Sample Size Determination for Cronbach's Alpha - PubMed If you are interested in examining how closely different evaluators are scoring the same student scripts, then I would stick to one of the statistics that are more commonly used to measure Inter-rater reliability. Med J Islam Repub Iran. Depression is recognized as the most common mental health disorder globally and is expected to be the leading cause of mortality by 2030 [2, 3]. The sample size was calculated based on an item-to-respondent ratio of 1:11 [32]. https://doi.org/10.1186/s12913-022-07514-4, DOI: https://doi.org/10.1186/s12913-022-07514-4. The prevalence of stress, anxiety and depression within front-line healthcare workers caring for COVID-19 patients: a systematic review and meta-regression. Don't have time for it all now? 12 As the estimate of reliability increases, the fraction of a test score that is attributable to error will decrease. Jamali J, Roustaei N, Ayatollahi SMT, Sadeghi E. Factors affecting minor psychiatric disorder in southern Iranian nurses: a latent class regression analysis. Disclaimer. 2005 Mar-Apr;31(2):162-73. doi: 10.1016/s0013-7006(05)82383-8. de Vet HCW, Mokkink LB, Mosmuller DG, Terwee CB. Use this statistic to help determine whether a collection of items consistently measures the same characteristic. The study was funded by Vice-chancellor for Research and Technology, Hamadan University of Medical Sciences (NO Grant: 9910167153). Cronbach's Alpha (a) The majority of these studies have reported good internal consistency and reliability [23,24,25,26,27]. An Example Suppose a restaurant manager wants to measure overall satisfaction among customers, so she sends out a survey with the following questions to which customers can respond strongly disagree, disagree, neutral, agree, or strongly agree. 2nd ed. The global burden of disease: 2004 update. I think you are the best person to whom I could write to get my query clarified. -. Streiner DL, Norman GR, Cairney J. A total of 1245 nurses completed this survey; however, 110 questionnaires were excluded, based on the inclusion and exclusion criteria. This study is part of a larger study examining the relationship between burnout and depression, anxiety, and stress, based on self-reports of patient care quality and adverse events among nurses in Iran. Based on alpha of 0.05, the minimum sample size requirement is 207 to be able to detect at least 80.0% power of the test. For example, let us consider that we are interested to know the extent of handicap of patients suffering from cervical myelopathy. Please enable it to take advantage of the complete set of features! On the other hand, the COVID-19 pandemic has an important role in the well-being of healthcare professionals, especially nurses [16]. For comparison of two coefficients of Cronbach's alpha, a larger sample size is needed when testing for smaller effect sizes. Alpha is very sensitive to how many items are included in a scale. If I follow the rule of one alpha per application, since each teacher rated their feedback in relation to each child, I would obtain: 3 teachers x 4. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. So adding 'I like Manchester United', 'Manchester United are the best soccer team', and 'Manchester United are great' as items to be responded to in a scale about self-efficacy in science learning would likely increase alpha. But, as I pointed out above, instruments often contain unrelated scales, and authors would sometimes calculate an overall alpha (the computer found to be greater than that of each of its component scales at least that would be the implication if it were assumed that a larger alpha means a higher internal consistency without factoring how alpha tends to be larger the more items are included in the calculation. Anyway. For example, in a questionnaire designed to measure optimism, there are typically many items that collectively measure the construct of optimism. The general rule of thumb is that a Cronbach's alpha of .70 and above is good, .80 and above is better, and .90 and above is best. Given the high prevalence of depression, anxiety, and other mental disorders in Iranian healthcare professions especially nurses and their different working environments, and conditions. 2007;73(5):336340. PubMed Manual sample size calculation using Microsoft Excel software and sample size tables were tabulated based on a single coefficient alpha and the comparison of two coefficients alpha. Explor Res Clin Soc Pharm. Akbari M, Bagheri A, Fathollahi A, Darvish M. Job satisfaction among nurses in Iran: does gender matter? 1). Available from: Springer Nature. 1. The World Health Organization (WHO) estimated that more than 300 million people suffer from depression worldwide. Although I did not think this was necessary, when the paper was reviewed for publication a journal reviewer felt the paper was too anecdotal: that just because a few papers included weak practice, that may not have been especially significant. The present results are consistent with previous validation studies of DASS-21 conducted in different countries in both medical and non-medical settings, which revealed that Cronbachs alpha was above the agreed cutoff point (0.70) [22,23,24,25,26, 29, 30, 58]. EK and SM designed and conducted the study, performed the analysis and drafted the manuscript. Drug Alcohol Depend. In Table 2 the results of the corrected item-total correlations and Cronbachs alpha coefficients for the index subscales, in addition to the mean scores and standard deviations (SDs) for the items and the three subscales (depression, anxiety, and stress) was presented. Hum Resour Health. If the assessment is a single essay-type question, there will still likely be a rubric which offers credit for a range of different things (perhaps structuring a response, knowledge demonstrated, clarity of argumentation, acknowledging different perspectives, originality, and so forth) so you are still interested in how different evaluators apply criteria in each of these areas, so I would still tend to think that Cronbach would not be a good choice. Gobbi G, Atkin T, Zytynski T, Wang S, Askari S, Boruff J, et al. View all posts by Keith. 2020;51:102073. Cronbach s Alpha - Measurement of Internal Consistency - Explorable It only makes sense to test the internal consistency of this instrument, looking to assess knowledge and understanding across a topic, if we really think that (e.g., knowledge and understanding of force, or whatever topic) was effectively a single construct. By using this website, you agree to our Except for the AGFI, the fit indices were lower than the cutoff points in our study. 2003. Subst Abuse Treat Prev Policy. 2023 Aug;52(8):1549-1565. doi: 10.1007/s10964-023-01772-z. (PDF) Cronbach's alpha reliability: Interval estimation, hypothesis Although DASS-21 has been used in different countries and translated into different languages, the Persian version of this scale has not been validated in medical populations in Iran. The Use of Cronbach's Alpha When Developing and Reporting Research This study reviews the sample size guideline for Cronbach's alpha test. 2017;30:568. However, when items are used to form a scale they need to have internal consistency. Seventy participants were randomly selected to complete the questionnaires; also, 57 participants completed the questionnaire again after 3 weeks. Cronbach's alpha, , which is the most common measure of scale reliability (This is a convenient way to think of Cronbach's alpha but see Field, 2005, for a more technically correct explanation). Psychol Med. Informed consent was also obtained from each participant for the survey. In general, CFA is a robust method of statistical analysis for examining a predetermined factor structure or hypothetical theory; it describes how well each item evaluates the scale dimensionality. I still think the paper would have made a contribution without the survey BUT the extra work did strengthen paper. They were also assured that the survey was voluntary and that they could withdraw from the study at any time. For comparison of two coefficients of Cronbach's alpha, a larger sample size is needed when testing for smaller effect sizes. Some professionals insist on a reliability score of 0.70 or higher in order to use a psychometric instrument. Reliability Analysis - Hanover College If we have two scales which each measure a distinct aspect, and combine them to form one long scale, alpha would probably be high, although the merged scale is obviously tapping two different attributes. But consider a scale with five items where everybody responds to each item in exactly the same way (not, that is, different people respond in the same way as each other, just whatever response a person gives to one item e.g., 2 on a scale of 1-7 they also give to the other items). In the present study, the internal consistency reliability and construct validity of the Persian DASS-21 were examined. Third, each item has no "right" answer, which makes the summated rating scale different . The items of the scale are rated on a four-point Likert scale, with the score for each item ranging from 0 (does not apply to me at all) to 3 (applies to me most of the time). You are right that in the paper I suggest that Cronbach is more suited to use in the affective domain, when the construct being considered is something like self-efficacy in or attitude to , rather than in the cognitive domain. The first problem is that alpha is dependent not only on the magnitude of the correlations among items, but also on the number of items in the scale. 2016;13(1):135. PDF Reliability Analysis - Discovering Statistics government site. Contemp Nurse. The fear of COVID-19 outbreak among health care professionals in Gaza strip, Palestine. In the present study, the RMSEA was calculated to be 0.078, and 2/df P-value was <0.001. Correspondence to Tonsing KN. doi: 10.1371/journal.pone.0286556. This leads directly to the second problem. Ng F, Trauer T, Dodd S, Callaly T, Campbell S, Berk M. The validity of the 21-item version of the depression anxiety stress scales as a routine clinical outcome measure. Moreover, the construct validity of DASS-21 was examined using a confirmatory factor analysis (CFA) to determine if the Persian version supports the three-factor construct of the original DASS-21. The goodness of fit was established based on the following fit indices: The Chi-square (2) goodness of fit should have a P-value >0.05; the comparative fit index (CFI) should be 0.90 [39]; the TuckerLewis index (TLI) should be >0.90 [40]; the root mean square error of approximation (RMSEA) should be 0.08 [40]; the goodness of fit index (GFI) and the adjusted goodness-of-fit index (AGFI) should be 0.85 [40], and the standardized root mean square residual (SRMR) should be 0.08 [40]. We can use the proc corr function to calculate Cronbach's Alpha: /*calculate Cronbach's Alpha*/ proc corr data=survey_data alpha; var Question1-Question3; run; The output tables provide us with a lot of information, but the main value we're interested in is the Raw value in the table titled Cronbach Coefficient Alpha. This is the first study, to the best of our knowledge, to examine the factor structure of the Persian DASS-21 for healthcare professionals. The association between life satisfaction and the extent of depression, anxiety and stress among Iranian nurses: a multicenter survey. Geneva: World Health Organization; 2017. p. 124. Int J Psychol. Sample size requirements for the design of reliability study: review and new results. Often, studies state that alpha is measuring reliability as internal consistency is sometimes considered a kind of reliability. Besides, some studies have reported acceptable RMSEA, including a study conducted in Turkey among health control and clinical samples (RMSEA=0.065) [24] and a study in Chinese hospital workers (RMSEA=0.075) [22]. Clipboard, Search History, and several other advanced features are temporarily unavailable. Retrieved Jun 30, 2023 from Explorable.com: https://explorable.com/cronbachs-alpha. How to Report Cronbach's Alpha? | ResearchGate She decides to send out a survey to 200 customers who can rate the restaurant on a scale of 1 to 5 for 12 different categories. Kakemam E, Kalhor R, Khakdel Z, Khezri A, West S, Visentin D, et al. Spearman-Brown prophecy formula and Cronbach's alpha: different faces of reliability and opportunities for new applications. The minimum accepted sample size was 231 participants. 2009;37(5):71726. (And consequently discovering that many of those using Cronbach did not seem to understand what it was intended for.). I could not get a reference for the above. [Development and validation of an instrument to measure the satisfaction of users of rehabilitation services]. 2019;55(2-3):23749. Generally, alpha coefficient ranges in value from 0 to 1 and may be used to describe the reliability of factors extracted from dichotomous (that is, questions with two possible answers) and/or multi-point formatted questionnaires or scales (i.e., rating scale: 1 = poor, 5 = excellent). Participating nurses were asked to send the link to other nurses in their departments and hospitals. The nurses were told that their information would remain anonymous. Fifty-seven nurses were included in the test-retest. Item development for patient-centered care preferences using a three-archetype heuristic: An exploratory study. Keith S. Taber What is Cronbach's alpha? J Youth Adolesc. Besides, corrected item-total correlations of the three subscales were calculated, which represent the correlation of each item with its subscale when the item is removed. The correlations between the dimensions of DASS-21 were evaluated by measuring Pearsons correlation coefficients. We used SPSS V.20.0 and AMOS V.21.0 software of Windows for statistical analysis. In many studies, CFA has been considered an important index for culturally adapted scales [38]. Iran J Psychiatry. Today, it is clear that nurses have one of the most stressful health occupations, with more mental health complaints than any other health professionals [8,9,10]. Cronbachs Alpha. The high prevalence of depression, anxiety, and stress is associated with worse patient care safety and health care quality [14], higher occurrence of adverse events [15]. Assessment. volume22, Articlenumber:111 (2022) Int J Environ Res Public Health. 2018;7(1):1930. How to Calculate, Interpret, and Report Cronbach's Alpha Reliability That seems wrong. A study among Iranian nurses demonstrated that anxiety, stress, and depression scores significantly increased during the first wave of the COVID-19 pandemic compared with before the COVID-19 outbreak [18]. We might feel that is a sufficiently unitary construct, and design an instrument with a range of items all intended to test whether students understand that force is measured in newtons. Factor structure of the depression anxiety stress Scale-21 (DASS-21): Unidimensionality of the Arabic version among Egyptian drug users. Current practice is to report the sample value of Cronbach's alpha. No problem, save it as a course and come back to it later. In retrospect, I am happy that I responded to review comments in that way as it did actually show just how frequency alpha is used in science education, and the wide variety of practice in reporting the statistic. Topics: Basic Concepts; Real Statistics Support; Hypothesis Testing and Confidence Intervals; Power and Sample Size Confirmatory analysis model with factor loadings and correlations for the three IR- DASS-21 subscales. Validation of DASS-21 among nursing and midwifery students in Brunei. For this reason the coefficient is also called the internal consistency or the internal consistency reliability of the test. Required fields are marked *. We did not use exploratory factor analysis (EFA) because as far as we knew, DASS-21 was developed using EFA [19]. Evidence suggests that these mental health problems are directly associated with social and physical problems, such as dysfunctional family relationships, high suicide rates, poor achievement, and use of illegal drugs [1, 5,6,7]. Authors often cite alpha values with little commentary to explain why they feel this statistic is relevant and seldom interpret the result for readers beyond citing an arbitrary threshold for an acceptable value. Table3 displays the test-retest reliability. 2008;2(2):82102. Your email address will not be published. Nursing research: generating and assessing evidence for nursing practice.
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