The content validity was determined using a qualitative and a quantitative method. First, based on the judgments of knowledgeable experts in tool design and psychologists and psychiatrists, the content validity of the tool was assessed. In the qualitative content validity assessment, the researchers asked ten experts to express their opinions after carrying out a qualitative assessment of the tool in terms of grammar, wording, necessity, importance, item allocation and proper scoring (
19). The quantitative content validity was determined using the content validity ratio (CVR) and the content validity index (CVI).To measure the CVR, the said ten experts were asked to rate each item based on a 3-point scale (from ‘necessary’ to ‘not necessary’). Then, if the number obtained from Lawshe’s table for determining the minimum value of the index was greater than 0.62, the item was deemed necessary and important for the tool at the statistical significance level of P < 0.05 (
20). The CVI was evaluated based on the Waltz and Bausell CVI (
19). The experts were asked to determine the relevance, simplicity and clarity of each item in the questionnaire. These three criteria were separately assessed by the experts for each item using a 4-point Likert scale. If the CVI of an item was greater than 0.79, the item was deemed appropriate, if the score was 0.75 - 0.80, the item was deemed questionable, and if the score was less than 0.70, the item was deemed unacceptable and had to be eliminated from the tool (
21). In the next step, based on the mean CVI of all the questionnaire items, the mean scale-level content validity index/average(S-CVI/Ave) of the questionnaire was calculated. Polit et al. have recommended a score of 90% or higher for accepting the S-CVI/Ave (
22).