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help for imputemok                                         Jean-Benoit Hardouin
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Imputation of missing item responses with the Mokken scaling

        imputemok varlist [,prefix(string) max(#)]


Description

    imputemok imputes missing item responses with the Mokken scaling as
    defined in Huisman and Molenaar (2001). This module runs only with
    dichotomous items.

    The following algorithm is used:

        First, the items are ordered according to the percentage of positive
    responses (in a decreasing order).

        For each individual, if a positive response follows a missing
    response, it is imputed to 1.

        Else if a negative response precedes a missing response, it is
    imputed to 0.

        Else we count the number of positive and negative responses preceding
    a missing response and if the number of negative response is larger or
    equal than the number of positive responses, the missing value is imputed
    to 0.

        Else we count the number of positive and negative responses following
    a missing response and if the number of positive response is larger or
    equal than the number of negative responses, the missing value is imputed
    to 1.

        Else, the missing value is imputed by drawing a random number based
    on the observed proportion of positive responses to the item.

Options

    prefix defines the prefix to use to name the imputted variables (this
        prefix is followed by the name of the initial variable). By default,
        this prefix is "imp".

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

Example

        . imputemok itemA*

        . imputemok itemA*,prefix(new)


Reference

    Huisman M. and Molenaar I. W., Imputation of missing scale data with item
        response models. In A. Boomsma, M.A.J. van Duijn, & T.A.B. Snijders
        (Eds.), Essays on item response theory (pp. 221-244).  New York:
        Springer-Verlag, 2001.

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