get_tau {dscore}

Obtain difficulty parameters from item bank

Description

Searches the item bank for matching items, and returns the difficulty estimates. Matching is done by item name. Comparisons are done in lower case.

Usage

get_tau(items, key = NULL, itembank = dscore::builtin_itembank)

Arguments

items

A character vector containing names of items to be included into the D-score calculation. Milestone scores are coded numerically as 1 (pass) and 0 (fail). By default, D-score calculation is done on all items found in the data that have a difficulty parameter under the specified key.

key

A string that selects a subset in the itembank that makes up the key, the set of difficulty estimates from a fitted Rasch model. The built-in keys are: "gsed2212" (default), "gsed2208" (deprecated), "gsed2206" (deprecated), "gsed1912", "lf2206", "sf2206", "gcdg", and "dutch". Since version 1.5.0, the key = "gsed" selects the latest key starting with the string "gsed". Use key = "" to use all item names, which should only be done if there are no duplicate itemnames in the itembank.

itembank

A data.frame with columns key, item, tau, instrument, domain, mode, number and label. Only columns item and tau are required. The function uses dscore::builtin_itembank by default.

Value

A named vector with the difficulty estimate per item with length(items) elements.

Author(s)

Stef van Buuren 2020

See Also

builtin_itembank(), dscore()

Examples

# difficulty levels in the GHAP lexicon
get_tau(items = c("ddifmd001", "DDigmd052", "xyz"))