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99 lines
3.4 KiB
Plaintext
99 lines
3.4 KiB
Plaintext
8 months ago
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{smcl}
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{* Mars 2012}{...}
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{hline}
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help for {hi:pcmtest}
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{hline}
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{title:Global and item specific tests of fit for a Partial Credit Model or a Rating Scale Model}
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{p 8 14 2}{cmd:pcmtest}, [{cmdab:g:roup}({it:numlist})
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{cmdab:ne:w}
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{cmdab:nf:it}(#)
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{cmdab:p:ower}(#)
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{cmdab:a:lpha}(#)
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{cmdab:ap:proximation}
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{cmdab:s:itest}
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{cmdab:graph:ics}
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{cmdab:file:graph}({it:filegraph[, replace])]
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{title:Description}
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{p 8 14 2}{cmd:pcmtest} allows testing the fit between observed data and a
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partial credit model or a rating scale model.{p_end}
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{p 14 14 2}The global test of fit (test R1m) can only be computed if the data
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contains at least two items. Item specific test of fit (Si tests) can only be
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computed if the data contains at least three items. {p_end}
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{p 14 14 2}{cmd:pcmtest} is only performed if item difficulties have been
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estimated using {cmd:pcmodel}. {cmd:pcmtest} can be performed whether covariates
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have been included in {cmd:pcmodel} or not.
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{title:Options}
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{p 4 8 2}{cmd:group} specifies groups of scores, by defining the upper limit of
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each group
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{p 4 8 2}{cmd:new} allows changing the computation methodology of the pattern
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response probabilities between several tests of fit, rather than using the pattern
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response probabilities stored in Stata memory.
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{p 4 8 2}{cmd:nfit} specifies the size of a virtual sample with items response
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distribution strictly identical to that observed ({cmd:nfit} can deal with
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over-power problems when fit tests are performed on large samples).
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{p 4 8 2}{cmd:power} specifies the desired power for a R1m test, and estimates the
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corresponding size of a virtual sample with items response distribution strictly
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identical to that observed.
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{p 4 8 2}{cmd:alpha} specifies the type I error used to perform the test of fit
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(default: 0.05).
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{p 4 8 2}{cmd:approximation} Computation of the pattern response probabilities using
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simulation instead of Gauss Hermitte quadratures. Computation should be quicker for
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high number of items or responses categories.
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{p 4 8 2}{cmd:sitest} performs item specific test of fit (Si tests).
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{p 4 8 2}{cmd:graphics} displays several graphs (Distribution of the latent trait
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depending on the individual scores, graphic of MAP, graphic of
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the groups contributions to the R1m statistic, and graphic of the observed and expected
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score distribution).
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{p 4 8 2}{cmd:filegraph} indicates the filename and path for saving the graphs
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(four graphs are store: {it:filegraph}_LT_Sc, {it:filegraph}_MAP, {it:filegraph}_Contrib
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and {it:filegraph}_Score_Distrib.)
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{title:Outputs}
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{p 4 8 2}{cmd:e(globalFitTot)}: Results of the R1m test performed on the observed sample.
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{p 4 8 2}{cmd:e(itemFitTot)}: Results of the Si tests performed on the observed sample.
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{p 4 8 2}{cmd:e(globalFitPo)}: Results of the R1m test corresponding
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to the indicated power.
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{p 4 8 2}{cmd:e(itemFitPo)}: Results of the Si tests corresponding
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to the indicated power.
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{p 4 8 2}{cmd:e(globalFitTot)}: Results of the R1m test corresponding
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to the indicated sample size.
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{p 4 8 2}{cmd:e(itemFitTot)}: Results of the Si tests corresponding
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to the indicated sample size.
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{title:Author}
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{p 4 8 2}Jean-François Hamel{p_end}
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{p 4 8 2}Email:
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{browse "mailto:jeanfrancois.hamel@chu-angers.fr":jeanfrancois.hamel@chu-angers.fr}{p_end}
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{title:Also see}
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{p 4 13 2}Online: help for {help pcmodel}, {help gllamm}, {help simirt}
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, {help raschtest}.{p_end}
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