Item Information.

Item information in item response theory.

Usage

itemInformation(a = 1, b, c = 0, d = 1, theta)

Arguments

a

Discrimination parameter (slope).

b

Difficulty (severity) parameter (inflection point).

c

Guessing parameter (lower asymptote).

d

Careless errors parameter (upper asymptote).

theta

Person's level on the construct.

Value

Amount of item information.

Details

Estimates the amount of information provided by a given item as function of the item parameters and the person's level on the construct (theta).

See also

doi:10.1177/0146621613475471

Other IRT: deriv_d_negBinom(), discriminationToFactorLoading(), fourPL(), reliabilityIRT(), standardErrorIRT(), test_info_4PL()

Examples

itemInformation(b = 2, theta = -4:4) #1PL
#> [1] 0.002466509 0.006648057 0.017662706 0.045176660 0.104993585 0.196611933
#> [7] 0.250000000 0.196611933 0.104993585
itemInformation(b = 2, a = 1.5, theta = -4:4) #2PL
#> [1] 0.0002776035 0.0012430644 0.0055496459 0.0244490169 0.1016474844
#> [6] 0.3355795172 0.5625000000 0.3355795172 0.1016474844
itemInformation(b = 2, a = 1.5, c = 0.10, theta = -4:4) #3PL
#> [1] 3.079509e-07 6.153641e-06 1.208112e-04 2.200035e-03 3.040755e-02
#> [6] 2.085541e-01 4.602273e-01 2.954296e-01 9.102953e-02
itemInformation(b = 2, a = 1.5, c = 0.10, d = 0.95, theta = -4:4) #4PL
#> [1] 2.746997e-07 5.490237e-06 1.078762e-04 1.971020e-03 2.750508e-02
#> [6] 1.903184e-01 4.074248e-01 2.218341e-01 4.038413e-02