item_difficulty {performance} | R Documentation |
Difficulty of Questionnaire Items
Description
Compute various measures of internal consistencies for tests or item-scales of questionnaires.
Usage
item_difficulty(x, maximum_value = NULL)
Arguments
x |
Depending on the function, |
maximum_value |
Numeric value, indicating the maximum value of an item.
If |
Details
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.
Value
A data frame with three columns: The name(s) of the item(s), the item difficulties for each item, and the ideal item difficulty.
References
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
Examples
data(mtcars)
x <- mtcars[, c("cyl", "gear", "carb", "hp")]
item_difficulty(x)