View source: R/item_difficulty.R
item_difficulty | R Documentation |
Compute various measures of internal consistencies for tests or item-scales of questionnaires.
item_difficulty(x, maximum_value = NULL)
x |
Depending on the function, |
maximum_value |
Numeric value, indicating the maximum value of an item.
If |
Item difficutly of an item is defined as the quotient of the sum
actually achieved for this item of all and the maximum achievable score.
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 is 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.
Bortz, J., and Döring, N. (2006). Quantitative Methoden der Datenerhebung. In J. Bortz and N. Döring, Forschungsmethoden und Evaluation. Springer: Berlin, Heidelberg: 137–293
Kelava A, Moosbrugger H (2020). Deskriptivstatistische Itemanalyse und Testwertbestimmung. In: Moosbrugger H, Kelava A, editors. Testtheorie und Fragebogenkonstruktion. Berlin, Heidelberg: Springer, 143–158
data(mtcars)
x <- mtcars[, c("cyl", "gear", "carb", "hp")]
item_difficulty(x)
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