Skip to contents

The R-DIF scaling functions for item intercepts / thresholds.

d_fun.Rd

Computes the scaling function to be used from the item thresholds (d) in groups = {1, 2}. The options are:

  • type = 1: computes d.fun1 = (d2 - d1)/a1

  • type = 2: computes d.fun2 = (d2 - d1)/a2

  • type = 3: computes d.fun3 = (d2 - d1)/sqrt{(a1^2 + a2^2)/2}

Usage

d_fun(mle, type = 3)

Arguments

mle

the output of get_model_parms

type

a number in 1:3 indicating which version of delta to compute. See description for details.

Value

The vector of scaling function values.

Details

Computes (d2 - d1)/a for each threshold (d) of each item in groups g = {1, 2}. The parameter 'a' depends on the value of type: