Background and Objectives: Accurate measurement of the employees’ satisfaction with their office chairs can provide valid feedback on the chair design quality for the manufacturers and researchers. This study aims to design a valid and psychometrically evaluated questionnaire for measuring satisfaction with office chairs.
Methods: Through studying the two main documents about chair ergonomics including Iranian office chair standard No. 11388-1 and a valid Persian questionnaire on satisfaction with educational chairs (Mirmohammadi et al.), the initial 39-item office chair satisfaction questionnaire has been developed. Then face and content validity of the questionnaire have been checked out using qualitative and quantitative approach. Quantitative face validity was analyzed using impact score method. Content Validity Index (CVI) and Content Validity Ratio (CVR) have been used for quantitative content validity analysis. In order to analyze the questionnaire’s reliability, two methods including the internal consistency and constancy have been applied. To measure the internal consistency, α-Cronbach (alpha coefficient) and to evaluate constancy (test-retest) have been employed. Also, the receiver operating characteristic (ROC) curve was utilized for specifying its sensitivity, specificity, and cut-off point. The data was analyzed by SPSS 21 and Stata V.14
Results: Mean (CVR) and (CVI) of final questionnaire have been calculated as 0.93 and 0.95, respectively. Questionnaire’s α-Cronbach coefficient has been gained 0.8. Kappa coefficient (for inter-rater agreement) has showed high score (0.91) in the test-retest results, indicating high correlation and good constancy of the questionnaire. In the ROC, the cut-off point was reported as 75.5 with the sensitivity and specificity of 86.2 and 100, respectively, and area under the ROC curve at this cut-off point was 0.96.
Conclusion: The final 34-item questionnaire has exhibited acceptable reliability and validity for measuring satisfaction level of office chairs.
