Compute various measures of internal consistencies for tests or item-scales of questionnaires.
Depending on the function,
This function calculates the item difficulty, which should
range between 0.2 and 0.8. Lower values are a signal for
more difficult items, while higher values close to one
are a sign for easier items. The ideal value for item difficulty
p + (1 - p) / 2, where
p = 1 / max(x). In most
cases, the ideal item difficulty lies between 0.5 and 0.8.
A data frame with three columns: The name(s) of the item(s), the item difficulties for each item, and the ideal item difficulty.
data(mtcars) x <- mtcars[, c("cyl", "gear", "carb", "hp")] item_difficulty(x)
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