4PL-class

Three-Parameter Logistic IRT model

A collection of Item Response Theory (IRT) and Computerized
Adaptive Testing (CAT) functions that are used in psychometrics.

Emre Gonulates

Item Response Theory and Computerized Adaptive Testing Functions

4PL-class function

<dl>
<dt><code>a</code></dt>
<dd>Item discrimination parameter</dd></dl>
<dt><code>b</code></dt>
<dd>Item difficulty parameter</dd>
<dt><code>c</code></dt>
<dd>Guessing parameter</dd>
<dt><code>d</code></dt>
<dd>Upper-asymptote Parameter</dd>
<dt><code>D</code></dt>
<dd>Scaling constant</dd>
<dt><code>se_a</code></dt>
<dd>Standard error of item discrimination parameter</dd>
<dt><code>se_b</code></dt>
<dd>Standard error of item difficulty parameter</dd>
<dt><code>se_c</code></dt>
<dd>Standard error of guessing parameter</dd>
<dt><code>se_d</code></dt>
<dd>Standard error of upper-asymptote parameter</dd>

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Three-Parameter Logistic IRT model — 4PL-class

<dl>
<dt><code>a</code></dt>
<dd>Item discrimination parameter</dd>


<dt><code>b</code></dt>
<dd>Item difficulty parameter</dd>


<dt><code>c</code></dt>
<dd>Guessing parameter</dd>


<dt><code>d</code></dt>
<dd>Upper-asymptote Parameter</dd>


<dt><code>D</code></dt>
<dd>Scaling constant</dd>


<dt><code>se_a</code></dt>
<dd>Standard error of item discrimination parameter</dd>


<dt><code>se_b</code></dt>
<dd>Standard error of item difficulty parameter</dd>


<dt><code>se_c</code></dt>
<dd>Standard error of guessing parameter</dd>


<dt><code>se_d</code></dt>
<dd>Standard error of upper-asymptote parameter</dd>


</dl>

4PL-class: Three-Parameter Logistic IRT model

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