Evaluation of cross-cultural adaptation and validation of the Persian version of the critical thinking disposition scale: methodological study

This was a cross-sectional study utilizing cross-cultural adaptation to translate and investigate the validity and reliability of the CTDS for use among Iranian nursing students [20]. The translated scale underwent examination for reliability and validity tests.

Convenience sampling was employed at the School of Nursing, Shahid Beheshti University in Tehran. This method involved selecting participants who were readily available and willing to take part in the study. Specifically, the study targeted all undergraduate nursing students, who were invited to participate in the research. Recruitment continued until the desired sample size was achieved. To maintain the integrity of the data, students who submitted incomplete questionnaires were excluded from the analysis. Undergradute studies in Iran normally involve 4 years of education in general nursing, as well as clinical rotations in all hospital units and public health sectors.

There are two general recommendations concerning the minimum sample size necessary for conducting factorial analysis. The first recommendation emphasizes the significance of the absolute number of cases (N), while the second recommendation highlights the importance of the subject-to-variable ratio (p). Guilford suggested that N should be no less than 200 [21]. Additionally, MacCallum et al. recommended that the subject-to-variable ratio should be at least 5 [22]. A total of 390 nursing students voluntarily participated in the study.

The CTDS, developed by Sosu, is an instrument used to measure the dispositional dimension of critical thinking [23]. Self-report questionnaires were given to the students. The demographic questionnaire collected included participants’ age, gender, education, and grade point average (GPA). The Critical Thinking Disposition Scale (CTDS) was used to measure the dispositional aspect of critical thinking. This scale comprises 11 items, employing a five-point Likert-type response format (1 = strongly disagree; 2 = disagree; 3 = neutral; 4 = agree; 5 = strongly agree). Total scores range from 11 to 55. The subscores include the first seven items reflecting a level of critical openness with a score ranging from 7 to 35 and the last four items indicating a level of reflective skepticism with a score ranging from 4 to 20. Higher CTDS scores indicate a greater degree of critical thinking [23].

Following correspondence with the instroment developer, Dr. Sosu, and obtaining permission, the scale underwent translation using the standard Backward-Forward method. Initially, the scale was independently and simultaneously translated from English to Persian by two translators proficient in both Farsi and English. In the subsequent phase, these translations were juxtaposed and merged into a unified translation. This facilitated the comparison and identification of discrepancies, which were then rectified based on feedback from a panel of experts, including two psychometric experts and two nursing professors. In the third stage, the resulting Persian version was given to two translators fluent in Persian and English (distinct from those in the initial experts) to translate it back to English, thereby completing the translation of the scale from Persian to English. In the fourth stage, the two English translations were compared, and any disparities were resolved by the experts, culminating in a single translation. Subsequently, the prefinal version was evaluated for content and face validity.

Face validity refers to the degree to which a measurement method seems to accurately measure the intended construct [24]. In a qualitative assessment of face validity, 10 nursing students were asked to evaluate factors such as the clarity of phrases and words, the coherence and relevance of items, the potential for ambiguity, and the necessity of removing or combining items. Additionally, two nursing professors and two psychometric specialists scrutinized the scale to determine whether it indeed appeared to measure its intended construct.

Content validity examines the extent to which a collection of scale items aligns with the pertinent content domain of the construct it aims to assess [24]. The qualitative evaluation of the content validity involved a panel consisting of two nursing professors in the field of nursing education and two statisticians who were experts in psychometric topics. Their input on item placement, word selection, grammar adherence, and scoring accuracy of the scale and its instructions were solicited, with their feedback serving as the foundation for any required adjustments.

To explore the number of existing subscales and potential factors, Exploratory Factor Analysis (EFA) was performed using Principal Component Analysis (PCA) with varimax rotation. The scree plot and parallel analysis suggested the number of existing factors. The scree plot displays the eigenvalues of each factor extracted from the data in descending order. The number of factors was retained by examining the slope of the curve. A sharply decreasing slope indicates the optimal number of factors that capture the most variance in the data.

To confirm the findings of the EFA, Confirmatory Factor Analysis (CFA) was conducted using MPLUS to confirm the 2-factor structure identified with the items loaded on each factor in the EFA. Model fit indices, including Comparative Fit Index (CFI), the standardized residual root mean squared error (SRMR) of approximation and the root mean squared error of approximation (RMSEA), with cutoff points of > 0.95, < 0.08 and < 0.06, respectively, were used [25]. Factor loadings were reported using standardized beta coefficients to evaluate the strength of the relationships between items and factors, and a p value of 0.05 was considered a significant factor loading.

The mean scores for Critical Openness and Reflective Skepticism were computed. Convergent and Discriminant Validity was checked for correlations between students’ GPA as an indicator of academic achievement and the scores of the subscales of the CTDS.

To assess reliability, internal consistency was tested using Cronbach’s alpha coefficient calculations for the total score and subscores. To assess the consistency of the test-retest approach over a two-week period, a group of 40 individuals from the target demographic underwent examination. Their scores from both sessions were analyzed to determine test-retest reliability, and the Intraclass Correlation Coefficient (ICC) was calculated.

The current study underwent assessment and received approval from the Research Ethics Committee at Shahid Beheshti University of Medical Sciences (Ethical code: IR.SBMU.RETECH.REC.1403.013). Permissions were duly acquired from the pertinent authorities at the research sites as well as the developer of the original scale. Nursing students were provided with comprehensive information regarding the study’s objectives, their right to withdraw from participation, and the confidentiality of their data. Informed consent was obtained from all participating students. All procedures adhered strictly to the appropriate guidelines and regulations.

Descriptive statistics, including the mean, standard deviation, median, range, and frequency, were used to describe the population and their critical thinking scores. Analysis of demographic characteristics, EFA, and reliability tests were performed using IBM SPSS Statistics (Version 27). CFA was performed using MPLUS (Program Copyright © 1998–2017 Muthén & Muthén Version 8) software.

The scree plot and parallel analysis suggested a two-factor solution (Fig. 1), which accounted for 55% of the total variance in the scores (Table 1). Factor loadings revealed a clear factor structure, with items loading on two factors. The rotated factor loadings are presented in Table 2. The items clustered together on two distinct factors, with no cross-loadings observed.

The two factors were interpreted as follows: Factor 1, labeled “Critical Openness,” comprised items related to the level of critical openness; Factor 2, labeled “Reflective skepticism” included items reflecting the level of reflective skepticism. These factors align well with previously established dimensions.

The standardized factor loadings ranged from 0.61 to 0.77, Fig. 2, all of which were statistically significant (p < 0.001) (Table 3). These loadings provided further support for the factor structure identified in the EFA.

Convergent and discriminant validity were examined by determining factor scores based on item allocation. The analysis revealed a sample mean of 28.65 (SD = 2.7) for the Critical Openness factor and a mean of 16.8 (SD = 1.8) for Reflective Skepticism. A weak yet statistically significant correlation was observed between students’ GPA and their level of critical openness (r = 0.15, p = 0.003), indicating a slight association between academic performance and this aspect of cognitive disposition.

The reliability of the CTDS-P was assessed through rigorous statistical analysis. Internal consistency was robust, as indicated by a Cronbach’s alpha coefficient of 0.87 for the overall scale, demonstrating the coherence of the items within the measure. Subscale analysis revealed strong reliability, with values of 0.83 for critical openness and 0.80 for reflective skepticism, indicating the consistency of responses across different dimensions of the construct. Additionally, the scale exhibited excellent test-retest reliability, as evidenced by an Intraclass Correlation Coefficient (ICC) of 0.96, with a 95% confidence interval ranging from 0.93 to 0.98, suggesting high stability and consistency of the scores over time.