rsdif Files

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CODE IMPLEMENTING RATING SCALE DIF:\
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\'91rsdif.R\'92 implements rating scale DIF and rating scale DPF. \
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Required inputs to \'91rsdif.R\'92:\
    \'91items\'92 = a numeric vector of item measures with no NA.\
    \'91persons\'92 = a numeric vector of person measures with no NA.\
    \'91thresholds\'92 = a numeric vector of ordered rating category thresholds with no NA.\
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Optional inputs to \'91rsdif.R\'92:\
    \'91dpf\'92 = logical for calculating rating scale DPF instead of rating scale DIF (the default). \
              Default is FALSE.\
    \'91normpdf\'92 = logical for using a standard normal distribution instead of the logistic distribution (the\
                       default). Default is FALSE.\
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Output of \'91rsdif.R\'92 is a list whose elements are:\
    \'91DIF_up\'92 = a numeric vector of rating scale DIF criteria for each item in the upwards direction.\
    \'91DIF_down\'92 = a numeric vector of rating scale DIF criteria for each item in the downwards direction.\
    \'91DIF_average\'92 = overall average of all \'91DIF_up\'92 and \'91DIF_down\'92 criteria.\
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Output of \'91rsdif.R\'92 is changed to \'91DPF_up\'92, \'91DPF_down\'92 and \'91DPF_average\'92 if \'91dpf\'92 = TRUE\
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EXAMPLE OF USE:\
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# Generate a random set of item measures, person measures and ordered thresholds:\
IM = runif(100, -2, 2)\
PM = runif(500, -2, 2)\
TH = sort(runif(5, -2, 2))\
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# Calculate rating scale DIF\
A = rsdif(IM, PM, TH)\
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# Results are in:\
A$DIF_up\
A$DIF_down\
A$DIF_average\
\
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RESULTS OF MSD AND RSDIF ANALYSIS OF IVI-28:\
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\'91rsdif_IVI_28.RData\'92 contains a list called \'91RSDIF_results\'92 whose elements are:\
    \'91MSD_parameters_IVI_28\'92 = a list of parameters estimated by the Method of Successive \
                                                  Dichotomizations, or MSD, using the R package \'91msd\'92. Parameters\
                                                  include item measures, person measures and rating category \
                                                  thresholds used as inputs to the \'91rsdif.R\'92 program\
    \'91DIF_IVI_28\'92 = a list of estimated rating scale DIF criteria in both DIF directions for every item, as\
                            well as the overall DIF average (see output of \'91rsdif.R\'92).\
    \'91DPF_IVI_28\'92 = a list of estimated rating scale DPF criteria in both DPF directions for every person,\
                             as well as the overall DPF average.\
}