updateDesign function

Update design elements

A function that will update the object returned from findNextItem. This can be used to run the CAT session manually in a set-by-step manner.

updateDesign(x, new_item, new_response, updateTheta = TRUE)

Arguments

• x: an object of class 'mirtCAT_design' returned from the mirtCAT function when passing design_elements = TRUE
• new_item: a numeric vector indicating which items to select
• new_response: a numeric vector indicating the responses the the selected items
• updateTheta: logical; update the internal ability terms after the new item response has been added to the internal objects?

Returns

returns an object of class 'mirtCAT_design' with updated elements.

Examples

## Not run:

set.seed(1)
nitems <- 100
itemnames <- paste0('Item.', 1:nitems)
a <- matrix(rlnorm(nitems, .2, .3))
d <- matrix(rnorm(nitems))
dat <- simdata(a, d, 500, itemtype = 'dich')
colnames(dat) <- itemnames
mod <- mirt(dat, 1, verbose = FALSE)

# test defined in mirtCAT help file, first example
CATdesign <- mirtCAT(mo = mod, criteria = 'MI', design_elements = TRUE,
  start_item = 2)

# returns 2 in this case, since that was the starting item
findNextItem(CATdesign) 

# first iteration, no answered items
CATdesign$person$items_answered

# update when next item is item 2 and answered correctly
CATdesign <- updateDesign(CATdesign, new_item = 2, new_response = 1)
CATdesign$person$items_answered  # item 2 answered first
CATdesign$person$responses       # in item 2 element response was = 1 
CATdesign$person$thetas # current estimate
findNextItem(CATdesign) 

# determine next item if item 70 were also answered correctly next
CATdesign <- updateDesign(CATdesign, new_item = 70, new_response = 1)
CATdesign$person$items_answered  
CATdesign$person$responses       
findNextItem(CATdesign) 

# continue on, now with item 95 added next (answered incorrectly)
CATdesign <- updateDesign(CATdesign, new_item = 95, new_response = 0)
CATdesign$person$thetas
CATdesign$person$thetas_history
CATdesign$person$thetas_SE_history
findNextItem(CATdesign)
## End(Not run)

References

Chalmers, R., P. (2012). mirt: A Multidimensional Item Response Theory Package for the R Environment. Journal of Statistical Software, 48(6), 1-29. tools:::Rd_expr_doi("10.18637/jss.v048.i06")

Chalmers, R. P. (2016). Generating Adaptive and Non-Adaptive Test Interfaces for Multidimensional Item Response Theory Applications. Journal of Statistical Software, 71(5), 1-39. tools:::Rd_expr_doi("10.18637/jss.v071.i05")

See Also

mirtCAT, findNextItem

Author(s)

Phil Chalmers rphilip.chalmers@gmail.com