catR (version 1.0)

nextItem: Selection of the next item

Description

This command selects the next item to be administered, given the list of previously administered items and the current ability estimate, with the 'maximum information' criterion.

Usage

nextItem(itemBank, theta, out=NULL)

Arguments

itemBank

an item bank of class itBank sa output of the function createItemBank.

theta

numeric: the current value of the ability estimate.

out

either a vector of integer values specifying the items previously administered, or NULL (default).

Value

• A list with three arguments:
• item
  the selected item (identified by its number in the item bank).
• par
  the vector of item parameters of the selected item.
• info
  the value of the information function for the selected item and the current ability estimate.

Details

Currently only one ethod is available for selecting the next item to be administered in the adaptive test. For a given current ability estimate, the next item is selected (among the available items) as the one which maximizes the item information function (Baker, 1992). The most informative item is selected from the table of item informations provided by the bank of items specified with itemBank. The available items are those that are not specified in the out argument. By default, out is NULL, which means that all items are available.

References

Baker, F.B. (1992). Item response theory: parameter estimation techniques. New York, NY: Marcel Dekker.

See Also

createItemBank

Examples

# Loading the 'tcals' parameters 
 data(tcals)
 tcals <- as.matrix(tcals)
 
 # Item bank creation with 'tcals' item parameters
 bank <- createItemBank(tcals)

 # Selecting the next item, current ability estimate is 0
 nextItem(bank, 0) # item 63 is selected

 # Selecting the next item, current ability estimate is 0
 # and item 63 is removed
 nextItem(bank, 0, out=63) # item 10 is selected

 # Selecting the next item, current ability estimate is 0
 # and items 63 and 10 are removed
 nextItem(bank, 0, out=c(63,10)) # item 62 is selected