How is the item content validity index (I-CVI) calculated, and what is the acceptable threshold?

The item content validity index (I-CVI) is calculated by dividing the number of experts who rate an item as 3 or 4 on a 4-point relevance scale by the total number of experts rating the item. It is the proportion of experts in agreement about an item's relevance. An I-CVI of .80 is considered acceptable, and items with an I-CVI below .78 should be carefully scrutinized and either revised or discarded.

Experts rate each item on the instrument using a 4-point relevance scale, where 1 = not relevant, 2 = somewhat relevant, 3 = quite relevant, and 4 = highly relevant. For each item, the I-CVI equals the number of experts giving a rating of 3 or 4 divided by the total number of experts. For example, if 4 out of 5 experts judge an item as quite or highly relevant, the I-CVI is .80, which is considered acceptable. The source states that items with an I-CVI below .78 should be carefully scrutinized and either revised or discarded, suggesting that lower I-CVI values indicate the item may not adequately reflect the construct.