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help for imputerasch                                       Jean-Benoit Hardouin
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Imputation of missing binary variables by a Rasch model

        imputerasch varlist [, prefix(string) norandom saveproba(string)
              nbiteration(#) details max(#)]

        varlist is a list of two or more existing dichotomous variables.

Description

    imputerasch imputes missing binary data by a Rasch model.  The parameters
        of the Rasch model are estimated on complete data, then the missing
        data are imputed from the estimated probability for each individual
        to response to each item.  By default, the imputed value is a result
        of a random draw within a Bernouilli random variable with this
        probability used like parameter, but it is possible to affect more
        deterministically the value of the missing data (0 if p<0.5 and 1 if
        p>=.5) with the norandom option.  An iterative procedure can be run
        in a second time by estimating parameters of the Rasch model on
        existing and imputing data, and by eventually correcting missing data
        at each step (see the nbiteration option).  This procedure is stopped
        as soon the allowed maximal number of iterations is attained, or as
        soon the imputed values are stable.

Options

    prefix. The former variables (with missing data) are keeped. New
        variables are created by imputing new values to missing data.  The
        name of these new variables are the names of the former variables
        preeceded by the prefix defined in this option. By default, this
        prefix is "imp".

    norandom avoids to randomly draw the value of imputation (by default). A
        deterministic process is used : if the expected probability is <0.5,
        imputed value is 0, else imputed value is 1 (the old name of this
        option, nobinomial, continues to run).

    saveproba allows saving the expected probability in variables whose the
        names begin by the string defined in this option.

    nbiteration realizes an iterative procedure which is stopped as soon as
        the maximal number of iterations is attained, or as soon as the
        imputed data are stable.

    details gives details on the imputation.

    max allows imputing missing values only for individuals with a maximal
        number of missing values defined with this option.



Example

        . imputerasch item*

        . imputerasch item*, norandom saveproba(p) prefix(dataimputed) max(4)

        . imputerasch item1-item5, nbiteration(5) details


Author

    Jean-Benoit Hardouin, PhD, assistant professor
    EA 4275 "Biostatistics, Clinical Research and Subjective Measures in
        Health Sciences"
    University of Nantes - Faculty of Pharmaceutical Sciences
    1, rue Gaston Veil - BP 53508
    44035 Nantes Cedex 1 - FRANCE
    Email:  jean-benoit.hardouin@univ-nantes.fr
    Websites AnaQol and FreeIRT