[Content validity index in scale development].

Content validity is the degree to which an instrument has an appropriate sample of items for the construct being measured and is an important procedure in scale development. Content validity index (CVI) is the most widely used index in quantitative evaluation. There are 2 kinds of CVI: I-CVI and S-CVI. A method to compute a modified kappa statistic (K*) can be used to adjust I-CVI for chance agreement. S-CVI/UA and S-CVI/Ave are both scale level CVI with different formulas. Researchers recommend that a scale with excellent content validity should be composed of I-CVIs of 0.78 or higher and S-CVI/UA and S-CVI/Ave of 0.8 and 0.9 or higher, respectively. The characteristics and qualifications of the experts, process and main results of content validity evaluation should be reported in scale-related manuscript.