score.multiple.choice: Score multiple choice items and provide basic test statistics

Description

Ability tests are typically multiple choice with one right answer. score.multiple.choice takes a scoring key and a data matrix (or data.frame) and finds total or average number right for each participant. Basic test statistics (alpha, average r, item means, item-whole correlations) are also reported.

Usage

score.multiple.choice(key, data, score = TRUE, totals = FALSE, ilabels = NULL, missing = TRUE, impute = "median", digits = 2,short=TRUE)

Arguments

key

A vector of the correct item alternatives

data

a matrix or data frame of items to be scored.

score

score=FALSE, just convert to right (1) or wrong (0). score=TRUE, find the totals or average scores and do item analysis

totals

total=FALSE: find the average number correct total=TRUE: find the total number correct

ilabels

item labels

missing

missing=TRUE: missing values are replaced with means or medians mising=FALSE missing values are not scored

impute

impute="median", replace missing items with the median score impute="mean": replace missing values with the item mean

digits

How many digits of output

short

short=TRUE, just report the item statistics, short=FALSE, report item statistics and subject scores as well

Value

scoresSubject scores on one scale
missingNumber of missing items for each subject
item.statsscoring key, response frequencies, item whole correlations, n subjects scored, mean, sd, skew, kurtosis and se for each item
alphaCronbach's coefficient alpha
av.rAverage interitem correlation

Details

Basically combines score.items with a conversion from multiple choice to right/wrong.

The item-whole correlation is inflated because of item overlap.

Examples

Run this code

data(iqitems)
iq.keys <- c(4,4,3,1,4,3,2,3,1,4,1,3,4,3)
score.multiple.choice(iq.keys,iqitems)
#just convert the items to true or false 
iq.tf <- score.multiple.choice(iq.keys,iqitems,score=FALSE)
describe(iq.tf)  #compare to previous results