dif_loess: LOESS DIF method

In knickodem/WBdif: Investigate DIF and generate reports

LOESS DIF method

Description

Visual inspection of DIF with LOESS regression curves

Usage

dif_loess(item.data, dif.groups, match.type, match.scores)

Arguments

item.data	data frame of item responses with subjects in rows and items in columns
dif.groups	factor vector of group membership for which DIF is evaluated.
match.type	character indicating whether match.scores is a total summed score ("Total") or the summed score excluding the item under investigation ("Rest").
match.scores	A numeric vector (if match.type = "Total") or list of ncol(item.data) numeric vectors (if match.type = "Rest") of match scores used as a predictor in the LOESS regression.

Details

For each item in item.data, loess is called to regress the item responses on the scores supplied to match.scores. A separate model is run for each dif.groups level.

Value

A list containing:

• the plot of LOESS curves for each dif.groups level for every item in item.data

• the data used to generate the plot.

knickodem/WBdif documentation built on Feb. 3, 2024, 2:20 a.m.