dgp_uni: Data generating process for unidimensional rasch model

In lucasmanuelkohler/anchorpoint: Anchor Point Selection Based on the Gini Inequality Criterion

Description

Data generating process for unidimensional rasch model

Usage

dgp_uni(
  nobs,
  tlength,
  DIFpercent,
  DIFpattern = "balanced",
  DIFeffect = "constant",
  DIFamount = 0.6,
  ability = TRUE,
  sigmaable = c(1, 1),
  itemref = c(-2.522, -1.902, -1.351, -1.092, -0.234, -0.317, 0.037, 0.268, -0.571,
    0.317, 0.295, 0.778, 1.514, 1.744, 1.951, -1.152, -0.526, 1.104, 0.961, 1.314,
    -2.198, -1.621, -0.761, -1.179, -0.61, -0.291, 0.067, 0.706, -2.713, 0.213, 0.116,
    0.273, 0.84, 0.745, 1.485, -1.208, 0.189, 0.345, 0.962, 1.592)
)

Arguments

nobs	number of observations per group
tlength	interger > 0, test length (number of items)
DIFpercent	percentage of DIF items in the test
DIFpattern	"balanced": DIF balanced over groups "favorref","favorfoc": all DIF items favor one group
DIFeffect	data generating process for DIF effect: normal: item parameter differences are drawn at random from a normal distribution with mean DIFamount and sd = 0.1, like in Wang et al. (2012) uniform: item parameter differences are drawn at random from the vector [DIFamount-0.4,DIFamount-0.2,DIFamount,DIFamount+0.2,DIFamount+0.4] constant: item parameter differences are defined as DIFamount for all items
DIFamount	magnitude of DIF
ability	should the groups differ in mean ability? (default is TRUE)
sigmaable	positive numeric vector of length two, standard deviations for person parameter distributions in the two groups (default is c(1,1))
itemref	numeric vector of length tlength (if shorter, then sampling with replacement is used), item difficulty parameter for reference group like in Wang et al. (2012)

Value

list containing:

• dat: binary response matrix

• DIFindex: indicating which items were generated with DIF

• DIFside: which group is favored per item (-1 focal, 1 reference) default: focal group is favored for all items

• itemref: item difficulty parameter for reference group

• itemfoc: item difficulty parameter for focal group

• groups: group vector (factor),

References

• Wang WC, Shih CL, Sun GW (2012). “The DIF-Free-Then-DIF Strategy for the Assessmentof Differential Item Functioning.”Educational and Psychological Measurement,72(4), 687–708

Examples

# For examples, see ?getData.

lucasmanuelkohler/anchorpoint documentation built on April 16, 2021, 6:41 a.m.