Calculates the start item from age for an adaptive test to measure D-score.

Usage

dcat_start(
  txt = "",
  instrument = "gs1",
  key = "gsed2510",
  population = "",
  p = 50,
  session = "",
  format = "3.1",
  ...
)

Arguments

txt: A JSON string, URL, or file with BDS data in JSON format. Data should conform to the BDS JGZ 3.2.5 specification.
instrument: A character vector with 3-position codes of instruments that should match. The default is instrument = "gs1" for GSED SF; instrument = NULL allows for all instruments.
key: String. They key identifies 1) the difficulty estimates pertaining to a particular Rasch model, and 2) the prior mean and standard deviation of the prior distribution for calculating the D-score. The default key key = "gsed2510".
population: String. Name of the reference population.
p: percentage to pass the item, difficulty in percentile units.
session: Optional session key if data is already uploaded to sitehost.
format: JSON schema version, e.g., "3.0". Used when uploading.
...: Ignored

Value

A string of milestones.

Author

Iris Eekhout 2025

Examples

fn <- system.file("examples", "example_v3.1.json", package = "bdsreader")
dcat_start(txt = fn, p = 50)
#>                item
#> gs1cgc128 gs1cgc128
#>                                                                                                                                                                                                                label
#> gs1cgc128 SF128 Does your child understand the term 'longest'? For example, if you ask him/her to choose 'which is the longest of 3 objects?' (e.g. 3 spoons or sticks), would he/she be able to choose the longest?
#>             tau
#> gs1cgc128 73.47