The Item Response Theory framework encompasses a wide range of psychometric methods and mathematical models (latent trait models) to study individual responses to items defining a measurement instrument (multi-item scales such as questionnaires or tests) that is used to assess a specific construct ...
3
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1answer
61 views
IRT/Rasch modeling with very large N
I want to fit a 1-parameter IRT model on a questionaire with 15 questions and about six million people. Considering the large N, standard errors aren't essential. It looks like the IRT world is sort ...
4
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1answer
222 views
IRT in R: Does anyone know of an IRT item calibration function that can cope with NA's?
I have a dataset that looks like this.
...
2
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0answers
63 views
How to extract factor scores for each observation in IRT?
library(ltm)
fit <- rasch(LSAT)
factor.scores(fit)
This code can generate latent trait scores for response patterns. How can I extract latent trait scores for ...
0
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2answers
88 views
Error message from grm() in ltm: subscript out of bounds
I am analyzing a survey data set. One of the items in the survey is:
...
0
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0answers
66 views
Can anyone guide me on understanind the algorithm behind the R ltm method?
I am trying to understand the code behind R ltm method.
here are the lines written in the documentation of ltm method--
The parameters are estimated by maximizing the approximate marginal ...
1
vote
1answer
97 views
Error using ltm R package
I'm using the R package ltm to create a 2-parameter logistic regression.
The input matrix is sparse - many users have taken a small subset of the items in the item bank.
For some of my data sets i'm ...
1
vote
0answers
23 views
How do I extract difficulty and discrimination from a non-parametric IRT model
I've been using the KernSmoothIRT module in R to do non-parametric analysis of some items.
I'm trying to find a way to quantify the difficulty and discrimination ...
2
votes
1answer
98 views
Item information in IRT with item covariates (linear logistic test model)
Short question: How does the calculation and interpretation of IRT item information and test information change in the presence of item properties?
Long question: There's a variation on IRT called ...
2
votes
1answer
68 views
Item information in IRT
According to item information curves, item information for a 2PL IRT model is
$I(\theta)=a^2_i p_i(\theta) q_i(\theta)$
To determine $p_i(\theta)$ and $q_i(\theta)$, do you just use the observed ...
4
votes
1answer
137 views
Internal consistency reliability in item response theory models
How can internal consistency reliability of a test and of individual test items be quantified in Item Response Theory models? I know I can resort to Classical Test Theory, Cronbach's alpha, and other ...
1
vote
1answer
217 views
How to calculate absolute fit indices (RMSEA, GFI…) from relative ones (AIC, BIC…)?
I have conducted an IRT analysis with Conquest in order to compare two models (1-dimensional vs. 8-dimensional) applied to a given data set (41 items of a questionnaire, N=195).
Comparing the ...
2
votes
0answers
72 views
Testing graded response model thresholds for significance?
I have a data set in which two raters have each rated N samples using a 5-point ordinal rating scale. My primary interest is in whether these two raters make significantly different use of those ...
3
votes
0answers
98 views
Are discrimination parameters in two-parameter IRT models only specific to items?
Discrimination parameters in two-parameter model from IRT are usually considered item parameters.
But I've come to doubt it.
Think about psychophysics; for example, detecting luminance.
I don't ...
2
votes
0answers
165 views
Dealing with poor fit in an Item Response Theory model
I'm studying an online course with about 3000 students who each took several quizzes and I'm trying to apply Item Response Theory (using the ltm package in R) to model the questions, determine which ...
3
votes
1answer
134 views
Estimating ability using IRT when the model parameters are known
I have 3PL model parameters (guessing, difficulty and discrimination item parameters).
Is there any function with which I can estimate individual ability from item response data?
I tried the function ...
2
votes
1answer
94 views
Pros/cons of estimating parameters for missing observations?
Some people are playing a game online. Every time a person plays, a new game board is generated randomly. On generation of a new board, the player can also choose a special weapon. (The choice of ...
3
votes
3answers
256 views
Simulating responses to a test for item-response theory
I am developing an online assessment system and I need to calibrate the bank of questions but I do not have enough people to implement a pilot test. That is why I decided to simulate the responses of ...
11
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3answers
3k views
How to get started with applying item response theory and what software to use?
Context
I have been reading about item response theory, and I find it fascinating. I believe I understand the basics, but I am left wondering how to apply statistical techniques related to the area. ...
1
vote
3answers
477 views
Is there a package in R which implements the weighted maximum likelihood method?
Is there a package in R which implements the weighted maximum likelihood method (Warm, 1996) for estimating the person parameters in Rasch Models?
