tia function

Elementary test-item analysis

Elementary analysis of the items in a test and the test sumscores based on Classical Test Theory.

tia(choices, key, ...)

Arguments

• choices: The original responses to the items in the test: persons as rows, items as columns. May contain NA.
• key: A vector containing the key (correct answers) to the items in choices. If not given, the function will check if all data are either 0, 1, or NA: if yes, NA are recoded as 0, else an error message is returned.
• ...: Other parameters that may be passed to sco or cov

Returns

A list with three elements:

• testlevel: A list of statistics at test level (currently, only Cronbach's alpha, may be extended in future)
• itemlevel: A matrix showing, for each item, the proportion of correct responses, the correlation with the sum score, and the alpha that the test would have if the item were dropped.
• optionlevel: A matrix showing, for each possible choice in the multiple-choice item, the proportion of responses given, and the correlation with the sum score for the test (including the item). The correct response is highlighted with asterisks.

Examples

itemsum <- tia(Unscored, key=c(2,3,1,1,4,1,2,1,2,3,3,4,3,4,2,2,4,3))

Author(s)

Ivailo Partchev