ItemTotalCorr {exametrika} | R Documentation |
Item-Total Correlation
Description
Item-Total correlation (ITC) is a Pearson's correlation of an item with the Number-Right Score (NRS) or total score. This function is applicable only to binary response data.
The ITC is a measure of item discrimination, indicating how well an item distinguishes between high and low performing examinees.
Usage
ItemTotalCorr(U, na = NULL, Z = NULL, w = NULL, ...)
Arguments
U |
U is a data matrix of the type matrix or data.frame. |
na |
na argument specifies the numbers or characters to be treated as missing values. |
Z |
Z is a missing indicator matrix of the type matrix or data.frame |
w |
w is item weight vector |
... |
Internal parameters for maintaining compatibility with the binary data processing system. Not intended for direct use. |
Details
The correlation is calculated between:
Each item's responses (0 or 1)
The total test score (sum of correct responses)
Higher positive correlations indicate items that better discriminate between high and low ability examinees.
Value
A numeric vector of item-total correlations. Values typically range from -1 to 1, where:
Values near 1: Strong positive discrimination
Values near 0: No discrimination
Negative values: Potential item problems (lower ability students performing better than higher ability students)
Note
This function is implemented using a binary data compatibility wrapper and will raise an error if used with polytomous data.
Values below 0.2 might indicate problematic items that should be reviewed. Values above 0.3 are generally considered acceptable.
Examples
# using sample dataset
ItemTotalCorr(J15S500)