item_info | R Documentation |
Calculates Samejima's (1969) information for all items.
item_info(ermobject, theta = seq(-5, 5, 0.01))
i_info(hvec, itembeta, theta)
ermobject |
An object of class 'eRm'. |
theta |
Supporting or sampling points on the latent trait. |
hvec |
Number of categories of a single item. |
itembeta |
Cumulative item category parameters for a single item. |
The function item_info
calculates information of the
whole set of items in the 'eRm' object. The function i_info
does the same for a single item (and is called by item_info
).
Returns a list (i_info
) or a list of lists (where each list element
corresponds to an item, item_info
) and contains
c.info |
Matrix of category information in columns for the different theta values in rows. |
i.info |
Vector of item information for the different theta values. |
Thomas Rusch
Samejima, F. (1969) Estimation of latent ability using a response pattern of graded scores. Psychometric Monographs, 17.
The function to calculate the test information, test_info
and the plot function plotINFO
.
res <- PCM(pcmdat)
info <- item_info(res)
plotINFO(res,type="item")
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