How to Calculate Content Validity Ratios

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Worthless or essential -- that is the measurement of the Content Validity Ratio, or CVR. Struggling to find an empirical way to estimate an object's worth, C.H. Lawshe developed the CVR formula to rate how essential an object, product or employee is to the needs at hand. The formula is based on ratings from a group of experts in the field related to the object, product or person in question.

Assemble a group of experts, whose task it will be to rate an object, product or employee. Their answers can be "essential," "useful" or "not necessary." Group size can be as small as five, although the more opinions you receive, the more accurate the determination will be.

Tally the number of "essential" ratings for the object or person in question.

Use the following formula, using the total number of experts (N) and the number who rated the object as essential (E):

CVR = [(E - (N / 2)) / (N / 2)]

As an example, say you assembled a team of 10 experts, seven of whom rated the product essential:

CVR = [(7 - (10 / 2)) / (10 / 2)] CVR = [(7 - 5) / 5} CVR = 2 / 5 CVR = 0.40

Interpret the results. CVR can measure between -1.0 and 1.0. The closer to 1.0 the CVR is, the more essential the object is considered to be. Conversely, the closer to -1.0 the CVR is, the more non-essential it is.

In the example, the CVR was 0.40. While that number is positive, it does show doubt in the product. Had nine or 10 experts agreed that the item was useful, the result would be 0.80 or 1.0, respectively, which is much better. Conversely, if only one expert thought the item was useful, then the CVR would have been -0.80, which shows the item is not very essential.

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