The joint sample size is a matrix whose elements are the number of individuals who responded to each pair of items.
JointSampleSize(U, na = NULL, Z = NULL, w = NULL, ...)
Returns a matrix of class c("exametrika", "matrix") where each element (i,j) represents the number of students who responded to both item i and item j. The diagonal elements represent the total number of responses for each item.
U is a data matrix of the type matrix or data.frame.
na argument specifies the numbers or characters to be treated as missing values.
Z is a missing indicator matrix of the type matrix or data.frame
w is item weight vector
Internal parameters for maintaining compatibility with the binary data processing system. Not intended for direct use.