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Exercise

Content validity

Next, let's measure content validity using Lawshe's Content Validity Ratio (CVR). The lawshe data frame contains the ratings of three experts on five potential items. Print it in the Console to see more.

Remember that CVratio() takes two arguments: NTOTAL is the total number of experts, and NESSENTIAL is the number of experts indicating each item "Essential".

Let's use this function in conjunction with dplyr grammar from the prerequisite courses to calculate the CVR for each item in the lawshe data frame. This will be the CVR where NTOTAL is count of unique values in expert and NESSENTIAL is the sum of 'Essential' ratings for each item.

length(unique(expert)) will return a count of unique values in expert.

psychometric and dplyr have been loaded.

Instructions
100 XP
  • Group the data frame by the item variable.
  • Create a summary statistic for each grouped item.
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