The column index or name of data containing the variable
defining the rows of the contingency table. The variable
must have only two distinct values.
var2 : int or string
The column index or name of data containing the variable
defining the columns of the contingency table. The variable
must have only two distinct values.
strata : int or string
The column index of name of data containing the variable
defining the strata.
data : array-like
The raw data. A cross-table for analysis is constructed
from the first two columns.