Sample Size in Reliability Studies: A Practical Guide Based on Cronbach's Alpha

Introduction: During the last two decades, the concept of social capital has been used increasingly frequently in health sciences due to the direct and indirect relationships between social capital and populations' physical and mental health. Therefore, it is necessary to build an instrument to quantify this concept confidently and reliably. Objective: The study aimed to internal consistency and dimensionality of a seven-item scale to measure social capital in Colombia's general population of adults. Methods: An online validation study included a sample of 700 adults aged between 18 and 76 years; 68% were females. Participants completed a seven-item scale called the Cognitive Social Capital Scale (CSCS). Cronbach's alpha and McDonald's omega were computed to test internal consistency. The authors explore the internal consistency and dimensionality of the CSCS. Results: The CSCS presented a low internal consistency (Cronbach's alpha of 0.56 and McDonald's omega of 0.59) and poor dimensionality. Then, the researchers tested a five-item version (CSCS-5). The CSCS-5 showed high internal consistency (Cronbach's alpha of 0.79 and McDonald's omega of 0.80) and a one-dimension structure with acceptable goodness-of-fit indicators. Discussion: The CSCS-5 presents high internal consistency and a one-dimensional structure to measure cognitive capital social in the Colombian sample. Authors can recommend measuring social capital in the general Colombian population. Further research should corroborate this pencil and paper application findings and explore other reliability and validity indicators.

Asynchronous e-learning allows for targeted teaching, particularly advantageous when bedside and didactic education is insufficient. An asynchronous e-learning curriculum has not been studied across multiple centers in the context of a clinical rotation. We hypothesize that an asynchronous e-learning curriculum during the pediatric emergency medicine (EM) rotation improves medical knowledge among residents and students across multiple participating centers. Trainees on pediatric EM rotations at four large pediatric centers from 2012 to 2013 were randomized in a Solomon four-group design. The experimental arms received an asynchronous e-learning curriculum consisting of nine Web-based, interactive, peer-reviewed Flash/HTML5 modules. Postrotation testing and in-training examination (ITE) scores quantified improvements in knowledge. A 2 × 2 analysis of covariance (ANCOVA) tested interaction and main effects, and Pearson's correlation tested associations between module usage, scores, and ITE scores. A total of 256 of 458 participants completed all study elements; 104 had access to asynchronous e-learning modules, and 152 were controls who used the current education standards. No pretest sensitization was found (p = 0.75). Use of asynchronous e-learning modules was associated with an improvement in posttest scores (p < 0.001), from a mean score of 18.45 (95% confidence interval [CI] = 17.92 to 18.98) to 21.30 (95% CI = 20.69 to 21.91), a large effect (partial η(2) = 0.19). Posttest scores correlated with ITE scores (r(2) = 0.14, p < 0.001) among pediatric residents. Asynchronous e-learning is an effective educational tool to improve knowledge in a clinical rotation. Web-based asynchronous e-learning is a promising modality to standardize education among multiple institutions with common curricula, particularly in clinical rotations where scheduling difficulties, seasonality, and variable experiences limit in-hospital learning.

Objectives To assess the completeness of reporting of sample size determinations in unpublished research protocols and to develop guidance for research ethics committees and for statisticians advising these committees.Design Review...

BackgroundType 2 diabetes is a chronic but preventable disease that is on the rise among adolescents. Evaluating adolescents’ behavior and planning to prevent it require a valid and reliable instrument. This study aims at designing a psychometric instrument to measure adolescents’ behavior with respect to type-2 diabetes.Research Design and methodsIn this methodological research, 770 students (adolescent boys and girls aged 13–15 years) participated through multistage sampling. The Inclusion criteria were: junior high school students, students’ willingness for participation and not suffering from type-1 or type-2 diabetes. The questionnaire was designed by examining the relevant literature and the existing questionnaires as well as considering the research team’s comments. The validity of the study was determined through face validity and content validity both quantitatively and qualitatively. The construct validity was determined through exploratory and confirmatory factor analysis. Reliability was measured via intraclass consistency coefficient (ICC) and internal consistency reliability was measured by Cronbach Alpha. SPSS 16 and Eq. 6.1 were used for data analysis.ResultsAt first, a list of 47 initial items was designed and compiled, and after by removing similar (10 questions) or inappropriate sentences (12 questions), a draft questionnaire with 25 questions was designed. No items were removed in the face validity phase. Based on exploratory factor analysis, the number of items in the questionnaire was reduced to 20 items and was categorized in five dimensions of stress management, healthy food/healthy diet, unhealthy food/unhealthy diet, high-risk behavior, and self-care. The results of confirmatory factor analysis confirmed the model. The internal consistency coefficient was confirmed measuring Cronbach Alpha at 0.70 with ICC = 0.80.ConclusionThe questionnaire designed has standard psychometric properties to assess adolescents’ behavior with respect to type-2 diabetes prevention. The reliability and the validity of the questionnaire as well as its general structure were confirmed.

To estimate the reliability and validity of survey measures used to evaluate health plans and providers from the consumer's perspective. Members (166,074) of 306 U.S. health plans obtained from the National CAHPS Benchmarking Database 2.0, a voluntary effort in which sponsors of CAHPS surveys contribute data to a common repository. Members of privately insured health plans serving public and private employers across the United States were surveyed by mail and telephone. Interitem correlations and correlations of items with the composite scores were estimated. Plan-level and internal consistency reliability are estimated. Multivariate associations of composite measures with global ratings are also examined to assess construct validity. Confirmatory factor analysis is used to examine the factor structure of the measure. Plan-level reliability of all CAHPS 2.0 reporting composites is high with the given sample sizes. Fewer than 170 responses per plan would achieve plan-level reliability of .70 for the five composites. Two of the composites display high internal consistency (Cronbach's alpha > or = .75), while responses to items in the other three composites were not as internally consistent (Cronbach's alpha from .58 to .62). A five-factor model representing the CAHPS 2.0 composites fits the data better than alternative two- and three-factor models. Two of the five CAHPS 2.0 reporting composites have high internal consistency and plan-level reliability. The other three summary measures were reliable at the plan level and approach acceptable levels of internal consistency. Some of the items that form the CAHPS 2.0 adult core survey, such as the measure of waiting times in the doctor's office, could be improved. The five-dimension model of consumer assessments best fits the data among the privately insured; therefore, consumer reports using CAHPS surveys should provide feedback using five composites.

The aim was to translate, culturally adapt, and validate the APFQ (Australian Pelvic Floor Questionnaire) for the population of Brazilian pregnant and postpartum women. The translation and validation of the APFQ were performed according to Beaton's guideline recommendations, with a sample of 150 patients (75 pregnant, 75 postpartum). Cronbach's alpha assessed the scale's internal consistency and reproducibility with the intraclass correlation coefficient (ICC). To analyze the construct validity, two questionnaires were applied, and the Spearman correlation was performed. Confirmatory factor analysis (CFA) was executed to assess the fit of the data to the theoretical model. The ability to generate diagnosis was analyzed by sensitivity and specificity. Only 1% of the sample scored in the prolapse domain, so it was removed from the validation analyses. Cronbach's alpha values greater than 0.70 were obtained for the bladder and bowel domains, and 0.69 for sexual function. As for reproducibility, the ICC was greater than 0.75 for all domains. Spearman's correlation was good for bowel (r=0.74), moderate for bladder (r=0.58), and poor for sexual function (r=0.23). CFA results showed a non-optimal adherence: despite the Chi-squared value being significant (p<0.001), the CMIN- which is the adherence of the data to the model- value is less than 3. Sensitivity above 80% was obtained, whereas specificity of 43%, 16%, and 12% was obtained for bowel, bladder, and sexual functions respectively. The APFQ was translated, culturally adapted, and validated for Brazilian pregnant and postpartum women. It showed good indexes of internal consistency, construct validity, reproducibility, and sensitivity. However, the prolapse domain could not be validated.

This paper discusses the statistical principles, methods, and software programs used to calculate sample size. In addition, it reviews the practical challenges faced in calculating sample size. We show that because of such challenges, statistical calculations often do not provide us with a clear-cut number for the study sample size; rather they suggest a range of reasonable numbers. The paper also discusses several important nonstatistical considerations in determination of sample size, such as novelty of the study and availability of resources.

Objective(s): To evaluate the family physicians' practices and to measure its impact upon the quality of familymedicine health care in Baghdad City model primary health care centers.Methodology: A descriptive study, using the evaluation approach, has evaluated the impact of family physicians'practices upon quality of healthcare in Baghdad's Model Primary Health Care Centers of Family Medicine. It iscarried out during 15th of May – 20th of August 2017. The study is conducted at five model primary health carecenters of family medicine from two districts; AL-Rusafa and AL-Kurkh. Sample size is calculated to be (76)family physicians. Convenient sample of (124) patients who are attending these primary health care centers to seekfamily health care services. Adopted structured self-administered questionnaire is used to collect data from theFamily physicians. The list of dual-forced items obtained through the Delphi process, which include "Do" or "Don'tdo". Inpatient care is clarified with (25) statements, urgent care and minor procedures tested in (27) statements andambulatory care includes (16) statements. The quality of health care questionnaire is developed for the purpose ofthe study. The overall number of items included in the questionnaire is (18) items. Internal consistency "split-half"reliability is obtained through computation of Cronbach's alpha correlation coefficient. Content validity of thequestionnaire is determined through panel of (10) experts. Data are collected through the utilization of thequestionnaire and the interview technique as means of data collection. Data of both stages is entered to computerusing Statistical Package of Social Science, Version (23.00) for windows(10) (SPSS-23) and are handled usingdescriptive statistical data analysis approach (frequencies, percentages, mean of scores, total scores and Cronbach'salpha correlation coefficient) and inferential statistical data analysis approach (simple linear regression).Results: The study reveals that the majority of the family physicians has performance experienced inadequate offamily health care practices. The quality of family medicine health care services in Baghdad's primary health carecenters of the patients' perspectives is poor (82.30%).The impact of family physicians' practices upon the quality offamily medicine health care services in Baghdad City model primary health care centers presents that familyphysicians' practices have not made noteworthy change on the quality of family medicine health care services.Recommendations: Family physicians can follow the family medicine practices' standards to provide quality offamily medicine health care services. The Ministry of Health Department of Primary Health Care can periodicallymonitor the implementation of family physicians' practices standards for the benefit of better quality of familymedicine health care services. The family medicine quality of health care services can be valued on a regular basefor the benefits of the patients who are attending the primary health care centers to seek such care

Background: Learning motivation is the collective term for the internal and external factors that support or strengthen a learner's desire and willingness to acquire new knowledge. Every prospective teacher must acquire the skills necessary to do their job well, and learning is accelerated by learning motivation. Therefore, developing a standardised Learning Motivation Scale (LMS) is crucial for assessing the level of learning motivation among prospective teachers in West Bengal. The goal of the present study was to create a LMS to assess learning motivation level among prospective teachers.&#x0D; Method: Fifty (50) prospective teachers from West Bengal, India, were given a self-administered version of the LMS, which consists of twenty-eight (28) items, to collect the data. The learning motivation scale was subjected to item analysis following the data collection in order to remove the poor items. Following that, the final scale's internal consistency was evaluated using the 225 participants (prospective teachers) who participated in the Cronbach's alpha method.&#x0D; Result: The scale primarily consists of two subscales, intrinsic motivation and extrinsic motivation, each with twenty-eight (28) items measuring learning motivation. Following item analysis, the learning motivation scale's seven (7) poor items are eliminated in accordance with the discrimination index. As a result, 21 items from each of the two LMS subscales were kept. The scale's final iteration discovered 0.783 alpha values, a high level of statistically significant correlation.&#x0D; Conclusion: The findings indicate that the Scale is a useful tool that researchers and instructors can use to effectively gauge the level of learning motivation among prospective teachers.

This article is a narrative review that discusses the recommended sample size requirements to design a pilot study to assess the reliability of a questionnaire. A list of various sample size tables that are based on the kappa agreement test, intra-class correlation test and Cronbach's alpha test has been compiled together. For all calculations, type I error (alpha) was set at a maximum value of 0.05, and power was set at a minimum value of 80.0%. For the kappa agreement test, intra-class correlation test, and Cronbach's alpha test, the recommended minimum sample size requirement based on the ideal effect sizes shall be at least 15, 22, and 24 subjects respectively. By making allowances for a non-response rate of 20.0%, a minimum sample size of 30 respondents will be sufficient to assess the reliability of the questionnaire. The clear guideline of minimum sample size requirement for the pilot study to assess the reliability of a questionnaire is discussed and this will ease researchers in preparation for the pilot study. This study provides justification for a minimum requirement of a sample size of 30 respondents specifically to test the reliability of a questionnaire.

The development and psychometric testing of the Satisfaction with Simulation Experience Scale

Background/Aims:Psychotherapy research has continually placed emphasis on the role of the therapeutic relationship. The current provision of mental health care, however, is often carried out in a variety of contexts and involves a range of health professionals. Measures for assessing the therapeutic relationship provided in community settings by multidisciplinary mental health teams is therefore required. The aim of this study was to describe the development of the Norwegian version of the Scale To Assess the therapeutic Relationship (N-STAR) and to examine its reliability.Methods:A pilot study was conducted with clients with mental health issues (n=29) and mental health practitioners (n=29). Participants were recruited from a Norwegian community mental health setting and asked to complete the N-STAR. Data were analysed using T-tests, Cronbach's alpha, the Pearson correlation coefficient (r) and the intraclass correlation coefficient (ICC).Results:The internal consistency of the N-STAR total scale was good, whereas the subscales showed acceptable to questionable internal consistencies. There was a significant association between the total scores of clients and therapists (r = 0.42, p = 0.02), and the consistency in agreement between the clients' and the therapists' scores was good (ICC= 0.57, p = 0.02).Conclusion:The N-STAR total scale showed promising results in terms of its internal consistency and level of client-therapist agreement. Further research is needed to evaluate N-STAR measurement properties in larger samples in order to establish this method as a way of assessing and monitoring the therapeutic relationship in community mental health settings in Norway.

To validate and evaluate the reproducibility of a self-efficacy (SE) scale for adherence to antiretroviral therapy in children and adolescents with HIV/AIDS, taking into account the perspective of parents/guardians. The study was carried out at the Hospital-Dia, Centro de Referência e Treinamento em DST/AIDS (CRT/SP), in São Paulo, Brazil. The parents/guardians of 54 children and adolescents aged 6 months to 20 years were interviewed during routine consultations at our service. Data on SE were collected using the Self-Efficacy for Following Anti-Retroviral Prescription Scale, and SE scores were calculated in two different ways: factor analysis and a predefined formula. The scale's internal consistency was verified using Cronbach's alpha coefficient. Validity was tested by comparing the mean scores of a group of patients who did adhere to antiretroviral treatment with those of a group that did not (Mann-Whitney test) and by calculating the Spearman correlation coefficient for agreement between scores and clinical parameters. Reproducibility was verified using the Wilcoxon test, intraclass correlation coefficients (r(icc)) and Bland-Altman plots. The SE scale demonstrated good internal consistency (alpha = 0.87) and good reproducibility (r(icc) = 0.69 and r(icc) = 0.75). In terms of validity, the SE scale was capable of differentiating adherent patients from those who did not adhere to their antiretroviral treatment (p = 0.002) and exhibited a significant correlation with CD4 counts (r = 0.28; p = 0.04). The SE scale can be used to assess adherence to antiretroviral therapy in children and adolescents with HIV/AIDS, taking into account the perspective of parents/carers.

This study compared the reliability, validity, and responsiveness of self-reported measures of health related quality of life in recipients and non-recipients of workers' compensation who have carpal tunnel syndrome. Patients with carpal tunnel syndrome complete questionnaires at study enrollment and 6 months later scales measuring symptom severity functional status, and satisfaction were included. The scales internal consistency, validity, and responsiveness were assessed. The internal consistencies for each scale were high (Cronbach's alpha .88 to .96) and virtually identical in recipients and nonrecipients of workers' compensation. The correlations between self-reported and objectively measured grip strength were .32 in recipients and .30 in nonrecipients; these correlations were not influenced by whether workers' compensation recipients were out of work. Correlations between changes in scale scores and three indicators of perceived improvement were higher in recipients (.48 to .69) than in nonrecipients (.19 to .41) The reliability, validity, and responsiveness of these measures were comparable in nonrecipients and recipients of workers compensation, these data support the use of self-report measures in studies of workers.

P2-236: Functional assessment of communication skills for Alzheimer's disease