Content Validity Ratio

Validity is the degree to which an instrument measures what it is supposed to measure. Content validity (CV) determines the degree to which the items on the measurement instrument represent the entire content domain. Experts familiar with the content domain of the instrument evaluate and determine if the items are valid. A CV ratio (CVR) is a numeric value indicating the instrument’s degree of validity determined from expert’s ratings of CV. One rule of thumb suggests that a CVR of at least 0.78 is necessary to deem an item or scale as valid.

In order for a research study to provide accurate and meaningful results, the instrument used to test the hypothesis must be valid. Use of a measurement instrument that is not valid may produce meaningless results.

Methods to Calculate CVR

A CVR can be calculated for each item and overall for an instrument. There are two ways to calculate item and scale (overall) CVR. The first method was developed by Mary R. Lynn in 1986. Experts rate each item using a four-point ordinal scale (1 = not relevant, 2 = somewhat relevant, 3 = quite relevant, and 4 = highly relevant). The item CVR is calculated as the number of experts giving a rating of 3 or 4 divided by the total number of experts who evaluated the item. The scale CVR is a proportion of items that met validity (i.e., at least 0.78) out of the total number of items. Figure 1 provides an example of how to calculate item CVR using this method. Figure 2 depicts how to calculate a scale CVR using this method.

Figure 1 Example of calculating item content validity ratio (CVR)

Source: Lynn, M. R. (1986). Determination and quantification of content validity. Nursing Research, 35(6), 382–385.

Figure 2 Example of calculating scale content validity ratio (CVR)

Source: Lynn, M. R. (1986). Determination and quantification of content validity. Nursing Research, 35(6), 382–385.

A second method to calculate a CVR was developed by C. H. Lawshe in 1975. Experts rate each item using a four-point ordinal scale: 3 = essential; 2 = useful, but not essential; and 1 = not necessary. To calculate an item CVR, the following formula is used: CVR = (ne − N/2)/(N/2). In this ratio, ne is the number of content experts who indicated that the item was essential (i.e., a rating of “3”). N is the total number of content experts. The mean CVR of all items computes an overall scale CVR. Figure 3 provides an example of how to calculate item CVR using this method, while Figure 4 demonstrates how to calculate a scale CVR.

Figure 3 Example of calculating item content validity ratio (CVR)

Source: Lawshe, C.H. (1975). A quantitative approach to content validity. Personnel Psychology, 28, 563–575. doi:10.1111/j.1744-6570.1975.tb01393.x

Figure 4 Example of calculating scale content validity ratio (CVR)

Source: Lawshe, C.H. (1975). A quantitative approach to content validity. Personnel Psychology, 28, 563–575. doi:10.1111/j.1744-6570.1975.tb01393.x