search for: bilog

I have just submitted irtoys_0.1.0, a package potentially useful for those working with IRT models. It can fit the 1PL, 2PL, and 3PL models through a simple and unified syntax, using either the R package ltm, Brad Hanson's ICL program, or the commercially available BILOG-MG. The purpose is basically to facilitate teaching, and especially comparisons across models and/or programs. Various graphs, item fit statistics, scaling methods, ability estimation, simulation facilities etc. are also included. Please notice that most options in estimating an IRT model are...

I have just submitted irtoys_0.1.0, a package potentially useful for those working with IRT models. It can fit the 1PL, 2PL, and 3PL models through a simple and unified syntax, using either the R package ltm, Brad Hanson's ICL program, or the commercially available BILOG-MG. The purpose is basically to facilitate teaching, and especially comparisons across models and/or programs. Various graphs, item fit statistics, scaling methods, ability estimation, simulation facilities etc. are also included. Please notice that most options in estimating an IRT model are...

A new version of irtoys is / will be available on CRAN. Two minor bugs have been fixed. One of these is more interesting: the previous code did not anticipate negative estimates for discriminations. What I did not know is that, unlike ICL or Bilog, ltm does not constrain discriminations to be positive. This means that it can be used to analyze bipolar data (think political sciences). There are also two new features: (i) Tamaki Hattori has kindly provided me with the original 1980 article of Haebara, and he has written code for the symmetric...

Hello, my question is; for a specific item, how can I create a plot with both the empirical probability of correct response and the predicted probability as a function of the mean of the ability intervals (similar to a BILOG plot). Thank you -- View this message in context: http://r.789695.n4.nabble.com/IRT-ltm-function-plot-for-probabilities-tp2714881p2714881.html Sent from the R help mailing list archive at Nabble.com.

A new version of irtoys is / will be available on CRAN. Two minor bugs have been fixed. One of these is more interesting: the previous code did not anticipate negative estimates for discriminations. What I did not know is that, unlike ICL or Bilog, ltm does not constrain discriminations to be positive. This means that it can be used to analyze bipolar data (think political sciences). There are also two new features: (i) Tamaki Hattori has kindly provided me with the original 1980 article of Haebara, and he has written code for the symmetric...

..., lists, matrices, and other objects available in the package (irt.pars and sep.pars). Item parameters and calibration output can be summarized, and descriptive statistics for the item parameters can be displayed as well. There is also functionality for importing item and/or ability parameters from BILOG, PARSCALE, and TESTFACT (functionality for MULTILOG will be added in a later version). Getting Started: Running the separate calibration is generally a two-step process. The first step is to format the item parameters for processing with the function 'plink'. In the simplest scenario, para...

..., lists, matrices, and other objects available in the package (irt.pars and sep.pars). Item parameters and calibration output can be summarized, and descriptive statistics for the item parameters can be displayed as well. There is also functionality for importing item and/or ability parameters from BILOG, PARSCALE, and TESTFACT (functionality for MULTILOG will be added in a later version). Getting Started: Running the separate calibration is generally a two-step process. The first step is to format the item parameters for processing with the function 'plink'. In the simplest scenario, para...