Conceptual model for determining the effective size of the internal audit department

The research method of the present study is mixed and has been done with two types of qualitative and quantitative (mixed) approaches. In the qualitative part of the research, interview questions were compiled to collect data. Then the fuzzy Delphi questionnaire with a range of 7 degrees, ISM questionnaire and researcher-made questionnaire with a Likert scale of 5 degrees were used. The statistical population in the qualitative, fuzzy Delphi and ISM sections includes 13 managers and experts in the field of internal audit who were selected using purposive and non-probabilistic sampling methods and were conducted with in-depth and semi-structured interviews. Also, the statistical population of the quantitative section and for the validation of the final model included 384 auditors.The first step of the present study using the method of qualitative data analysis of the foundation (interview approach, summarizing and interpreting concepts and words with 3 types of open, axial and selective coding) has been used to identify the main and sub-categories of research.The final model was presented by extracting the main and sub-categories of the research using the results of qualitative data analysis of the foundation and ISM method. In total, the obtained model includes 10 main categories including internal audit size, human resource management, quality of the audit committee, description of internal audit tasks, comprehensive internal audit plan, corporate governance structure, internal audit mission, internal audit value, risk management and internal audit methodology and approach.