R: Score multiple choice items and provide basic test statistics

score.multiple.choice {psych}

R Documentation

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,skew=FALSE)

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 missing=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
`skew`	Should the skews and kurtosi of the raw data be reported? Defaults to FALSE because what is the meaning of skew for a multiple choice item?

Details

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

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

The example data set is taken from the Synthetic Aperture Personality Assessment personality and ability test at http://test.personality-project.org.

Value

`scores`	Subject scores on one scale
`missing`	Number of missing items for each subject
`item.stats`	scoring key, response frequencies, item whole correlations, n subjects scored, mean, sd, skew, kurtosis and se for each item
`alpha`	Cronbach's coefficient alpha
`av.r`	Average interitem correlation

Author(s)

William Revelle

Examples

data(iqitems)
iq.keys <- c(4,4,4, 6,6,3,4,4,  5,2,2,4,  3,2,6,7)
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

[Package psych version 1.7.8 ]