Abstract
The Impostor Phenomenon (IP) refers to persistent self-doubt and fear of being exposed as a fraud, despite evidence of competence. Although several instruments exist, many show limitations in cultural applicability, item clarity, and comprehensive representation of IP dimensions. Therefore, the present study aimed to develop and validate a new scale tailored for Pakistani medical students. An initial pool of 50 items was generated through an extensive literature review and insights from a qualitative study. Expert evaluation by five PhD-level professionals in related fields indicated good content validity (CVI = 0.90). For scale validation, data were collected from 900 medical students aged 18–25 years using a multistage stratified random sampling technique from eight medical colleges (four public, four private) across Lahore, Gujranwala, Gujrat, and Sialkot. For Exploratory factor analysis (EFA), initial form was administered on 450 medical students. It supported a nine-factor solution, with a Kaiser-Meyer-Olkin (KMO) value of 0.90, factor loadings above 0.40, communalities ranging from 0.50 to 0.80, and eigenvalues greater than 1.0, accounting for 68% of the total variance. Confirmatory factor analysis (CFA) was conducted on other 450 students which refined the model by removing five items with high modification indices and cross-loadings, resulting in a good model fit (RMSEA = 0.06, CMIN/DF = 2.59, CFI = 0.95, IFI = 0.95, TLI = 0.94, GFI = 0.82). Reliability analysis showed strong internal consistency (α = 0.83–0.93), excellent test–retest reliability (r = 0.98), and good convergent and divergent validity. These findings suggest that the ISS is a reliable and valid multidimensional instrument suitable for assessing impostor syndrome among medical students and can be applied in both research and educational interventions.