Hi everyone,<div><br></div><div>I was replicating the analyses of the examples in R.J De Ayala&#39;s IRT book. I tried to use different software packages including multilog, bilog mg, Mplus, IRTPRO, and R. When I tried to do 2PL analysis using the same data, I ended up with different results in Mplus. First I tried bilogmg as the author did and I got the same results but when I tried Mplus I ended up with the same results but with opposite signs. Negative estimations in bilogmg turned out to be positive in Mplus and positives turned out to be negative(see the output below). It is just reverse. </div>
<div><br></div><div>Does any of you guys know why this happens?</div><div><br></div><div>OUTPUT FROM BILOGMG</div><div><br></div><div><div>ITEM      INTERCEPT    SLOPE    THRESHOLD   LOADING   ASYMPTOTE    CHISQ     DF</div>
<div>              S.E.       S.E.       S.E.       S.E.       S.E.      (PROB)</div><div> -------------------------------------------------------------------------------</div><div> ITEM0001 |   <b>2.584</b>  |   1.226  |  -2.107  |   0.775  |   0.000  |   302.4   4.0</div>
<div>                |   0.044* |   0.047* |   0.056* |   0.030* |   0.000* | (0.0000)</div><div>                |             |             |              |             |             |</div><div> ITEM0002 |   <b>0.995</b>  |   1.992  |  -0.499  |   0.894  |   0.000  |   339.7   4.0</div>
<div>                |   0.032* |   0.061* |   0.013* |   0.027* |   0.000* | (0.0000)</div><div>                |             |             |              |             |             |</div><div> ITEM0003 |   <b>0.394</b>  |   1.551  |  -0.254  |   0.840  |   0.000  |   387.4   4.0</div>
<div>                |   0.022* |   0.041* |   0.014* |   0.022* |   0.000* | (0.0000)</div><div>                |             |             |              |          |          |</div><div> ITEM0004 |  <b>-0.416</b>  |   1.544  |   0.270  |   0.839  |   0.000  |   240.4   4.0</div>
<div>                |   0.021* |   0.039* |   0.014* |   0.021* |   0.000* | (0.0000)</div><div>                |              |             |            |              |             |</div><div> ITEM0005 | <b> -0.551</b>  |   0.983  |   0.560  |   0.701  |   0.000  |   461.2   4.0</div>
<div>                |   0.018* |   0.026* |   0.021* |   0.019* |   0.000* | (0.0000)</div><div> -------------------------------------------------------------------------------</div><div><br></div><div>OUTPUT FROM MPLUS</div>
<div><br></div><div><div>Thresholds</div><div>    U1$1              <b>-2.585</b>      0.038    -67.795      0.000</div><div>    U2$1              <b>-0.996</b>      0.030    -33.719      0.000</div><div>    U3$1              <b>-0.394</b>      0.021    -18.501      0.000</div>
<div>    U4$1              <b> 0.416</b>      0.022     19.266      0.000</div><div>    U5$1               <b>0.550</b>      0.018     30.164      0.000</div></div><div><br></div><div>Thanks,</div><div><br></div>-- <br><i><span style="font-family:georgia,serif">Sedat</span><span style="font-family:georgia,serif"><br>
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