cat_sim {xxIRT}

Simulation of Computerized Adaptive Testing (CAT)

Description

cat_sim runs a simulation of CAT. Use theta in options to set the starting value of theta estimate.

cat_estimate_mle is the maximum likelihood estimation rule. Use map_len to apply MAP to the first K items and use map_prior to set the prior for MAP.

cat_estimate_eap is the expected a posteriori estimation rule, using eap_mean and eap_sd option parameters as the prior

cat_estimate_hybrid is a hybrid estimation rule, which uses MLE for mixed responses and EAP for all 1's or 0's responses

cat_stop_default is a three-way stopping rule. When stop_se is set in the options, it uses the standard error stopping rule. When stop_mi is set in the options, it uses the minimum information stopping rule. When stop_cut is set in the options, it uses the confidence interval (set by ci_width) stopping rule.

cat_select_maxinfo is the maximum information selection rule. Use group (a numeric vector) to group items belonging to the same set. Use info_random to implement the random-esque item exposure control method.

cat_select_ccat is the constrained CAT selection rule. Use ccat_var to set the content variable in the pool. Use ccat_perc to set the desired content distribution, with the name of each element being the content code and tue value of each element being the percentage. Use ccat_random to add randomness to initial item selections.

cat_select_shadow is the shadow-test selection rule. Use shadow_id to group item sets. Use constraints to set constraints. Constraints should be in a data.frame with four columns: var (variable name), level (variable level, NA for quantitative variable), min (lower bound), and max (upper bound).

cat_stop_projection is the projection-based stopping rule. Use projection_method to choose the projection method ('info' or 'diff'). Use stop_cut to set the cut score. Use constraints to set the constraints. Constraints should be a data.frame with columns: var (variable name), level (variable level, NA for quantitative varialbe), min (lower bound), max (upper bound)

Usage

cat_sim(true, pool, ...)

cat_estimate_mle(len, theta, stats, admin, pool, opts)

cat_estimate_eap(len, theta, stats, admin, pool, opts)

cat_estimate_hybrid(len, theta, stats, admin, pool, opts)

cat_stop_default(len, theta, stats, admin, pool, opts)

cat_select_maxinfo(len, theta, stats, admin, pool, opts)

cat_select_ccat(len, theta, stats, admin, pool, opts)

cat_select_shadow(len, theta, stats, admin, pool, opts)

## S3 method for class 'cat'
print(x, ...)

## S3 method for class 'cat'
plot(x, ...)

cat_stop_projection(len, theta, stats, admin, pool, opts)

Arguments

true

the true theta

pool

the item pool (data.frame)

...

option/control parameters

len

the current test length

theta

the current theta estimate

stats

a matrix of responses, theta estimate, information and std error

admin

a data frame of administered items

opts

a list of option/control parameters

x

a cat object

Details

... takes a variety of option/control parameters for the simulations from users. min and max are mandatory for setting limits on the test length. User-defined selection, estimation, and stopping rules are also passed to the simulator via options.
To write a new rule, the function siganiture must be: function(len, theta, stats, admin, pool, opts). See built-in rules for examples.

Value

cat_sim returns a cat object

an estimation rule should return a theta estimate

a stopping rule should return a boolean: TRUE to stop the CAT, FALSE to continue

a selection rule should return a list of (a) the selected item and (b) the updated pool

Examples

## Not run: 
## generate a 100-item pool
num_items <- 100
pool <- with(model_3pl_gendata(1, num_items), data.frame(a=a, b=b, c=c))
pool$set_id <- sample(1:30, num_items, replace=TRUE)
pool$content <- sample(1:3, num_items, replace=TRUE)
pool$time <- round(rlnorm(num_items, mean=4.1, sd=.2))

## MLE, EAP, and hybrid estimation rule
cat_sim(1.0, pool, min=10, max=20, estimate_rule=cat_estimate_mle)
cat_sim(1.0, pool, min=10, max=20, estimate_rule=cat_estimate_eap)
cat_sim(1.0, pool, min=10, max=20, estimate_rule=cat_estimate_hybrid)

## SE, MI, and CI stopping rule
cat_sim(1.0, pool, min=10, max=20, stop_se=.3)
cat_sim(1.0, pool, min=10, max=20, stop_mi=.6)
cat_sim(1.0, pool, min=10, max=20, stop_cut=0)
cat_sim(1.0, pool, min=10, max=20, stop_cut=0, ci_width=2.58)

## maximum information selection with item sets
cat_sim(1.0, pool, min=10, max=20, group="set_id")$admin

## maximum information with item exposure control
cat_sim(1.0, pool, min=10, max=20, info_random=5)$admin

## Constrained-CAT selection rule with and without initial randomness
cat_sim(1.0, pool, min=10, max=20, select_rule=cat_select_ccat, 
        ccat_var="content", ccat_perc=c("1"=.2, "2"=.3, "3"=.5))
cat_sim(1.0, pool, min=10, max=20, select_rule=cat_select_ccat, ccat_random=5,
        ccat_var="content", ccat_perc=c("1"=.2, "2"=.3, "3"=.5))

## Shadow-test selection rule
cons <- data.frame(var='content', level=1:3, min=c(3,3,4), max=c(3,3,4))
cons <- rbind(cons, data.frame(var='time', level=NA, min=55*10, max=65*10))
cat_sim(1.0, pool, min=10, max=10, select_rule=cat_select_shadow, constraints=cons)

## Projection-based stopping rule
cons <- data.frame(var='content', level=1:3, min=5, max=15)
cons <- rbind(cons, data.frame(var='time', level=NA, min=60*20, max=60*40))
cat_sim(1.0, pool, min=20, max=40, select_rule=cat_select_shadow, stop_rule=cat_stop_projection, 
        projection_method="diff", stop_cut=0, constraints=cons)

## End(Not run)