Interdisciplinary Teaching Design Self-Efficacy Scale: The validity and reliability study

The aim of this study is to develop a valid and reliable instrument to assess teachers’ self-efficacy in designing interdisciplinary teaching. During the scale development process, the scaling by cumulative sums approach based on participant responses was employed. Validity evidence was gathered through content and construct validity procedures. An item pool was generated based on focus group interviews and a comprehensive literature review, followed by expert review for content validation. The study sample comprised 350 teachers for exploratory factor analysis (EFA) and 231 teachers for confirmatory factor analysis (CFA). The final version of the scale obtained through analyses consists of 21 items measured on an 11-point scale ranging from 0 to 100, structured under two factors, namely, Competencies and Challenges. The scale demonstrated high reliability, with Cronbach's alpha coefficients of 0.95 and 0.92 for the respective factors. The total variance explained by the two subscales collectively is 66.21%. The confirmatory factor analysis (CFA) yielded satisfactory model fit, with all goodness-of-fit indices meeting the recommended thresholds for acceptable to excellent fit, supporting the structural validity of the model χ² =1413.84, df=516, (χ²/df=2.74), RMSEA=.09, CFI=.92, RFI=.86, NNFI= .92, SRMR =.05. These findings provide robust evidence that the scale is a scientifically and psychometrically valid and reliable instrument for assessing teachers’ self-efficacy in designing interdisciplinary instruction.