Development and psychometric evaluation of the medication preparation and calculation self-efficacy scale for nursing students: a methodological study

Background Medication preparation and dose calculation are critical components of safe medication administration, requiring nursing students to integrate knowledge, skills, and clinical decision-making competencies. Assessing students’ self-efficacy in these processes is important for identifying their educational requirements. Therefore, measurement tools that can comprehensively assess this multidimensional construct are required. This study aimed to develop the Medication Preparation and Calculation Self-Efficacy Scale and examine its psychometric properties to assess nursing students’ self-efficacy regarding the medication preparation and calculation process. Methods This methodological study included 539 nursing students from two universities, with independent samples used for EFA and CFA. The scale items were developed based on a literature review and Bandura’s self-efficacy theory. Content validity was evaluated using the Delphi technique with input from 15 experts in the field. Construct validity was examined using Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA). Convergent and discriminant validity were assessed using Composite Reliability (CR), Average Variance Extracted (AVE), and the Fornell–Larcker criterion. Cronbach’s alpha and intraclass correlation coefficients (ICC) were calculated for reliability analyses. Criterion-related validity was evaluated using a five-item medication calculation test. Results The content validity index values for the scale ranged from 0.87 to 1.00 at the item level and were 0.97 at the scale level. The EFA revealed a three-factor structure that explained 63.72% of the total variance. Following the EFA and subsequent CFA-based model refinement, the initial 55-item scale was reduced to a final 29-item, three-factor structure. The CFA results indicated that the final model demonstrated an acceptable fit (χ²/df = 2.735, CFI = 0.918, TLI = 0.911, GFI = 0.907, AGFI = 0.904, NFI = 0.913, IFI = 0.908, SRMR = 0.055, RMSEA = 0.077). The CR values ranged from 0.937 to 0.941, and the AVE values ranged from 0.646 to 0.697, supporting convergent validity. Discriminant validity was also supported by the Fornell–Larcker criterion. Cronbach’s alpha coefficients ranged from 0.918 to 0.949 for the factors and were 0.965 for the overall scale. In the criterion-related validity analysis, a moderate, positive, and statistically significant correlation was found between the total scale score and the medication calculation test score ( r = 0.412, p < 0.001). The test–retest analysis indicated that the scale demonstrated a good level of temporal stability (ICC = 0.89; 95% CI: 0.79–0.95). Conclusions The findings provide psychometric evidence supporting the use of the MPCSES for assessing nursing students’ self-efficacy in medication preparation and calculation. The final 29-item, three-factor structure enables the assessment of distinct but related dimensions of self-efficacy in medication management.