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