df: a data frame of individual survey data, where each row is an individual
vars_metric: a character vector of items to use in the Rasch Analysis
split_strategy: a named list giving the strategy to take for splitting variables by categories, passed to rasch_split(). One element of the list per variable to split by. Each element of the list must be a character vector of column names to split. The names of the list are the variables to split each group of variables by. Default is NULL, to not split items.
max_values: a tibble with two columns, var equivalent to vars_metric and max_val with their corresponding maximum possible values
Returns
a named list with: - df: new df after splitting the desired variables
vars_metric: new vars_metric after splitting the desired variables
max_values: new max_values after splitting the desired variables
Details
If significant differential item functioning (DIF) is observed, it may be desirable to split variables based on the characteristic for which DIF is observed. For example, if men and women have significantly different patterns of responses to items, then it may be desirable to split items by sex. This function performs that variable splitting.