Plot multiple-choice option curves — plot

The proportion choosing each response option across class intervals of the rest measure (the person estimate from the other items), with the keyed option drawn solid and bold. The keyed option should rise with the trait and every distractor should fall; a rising distractor is the graphical signature of a miskey or an ambiguous option.

Usage

plot_distractors(fit, item, n_groups = fit$n_groups)

Arguments

fit: A fitted object from rasch run with a key.
item: Keyed item name.
n_groups: Number of class intervals.

Value

Called for its plotting side effect; invisibly NULL.

Examples

set.seed(1); Np <- 400
th <- rnorm(Np)
raw <- sapply(seq(-1, 1, length.out = 6), function(d) {
  ok <- rbinom(Np, 1, plogis(th - d))
  ifelse(ok == 1, "A", sample(c("B", "C", "D"), Np, replace = TRUE))
})
colnames(raw) <- paste0("M", 1:6)
fit <- rasch(raw, key = setNames(rep("A", 6), colnames(raw)))
plot_distractors(fit, "M3")