During the JMLE estimation procedure, the measure estimates are improved each traversal of the data. The changes to the item and person estimates are computed by comparing the observed scores against the expected scores based on the current estimates. The changes are computed by curve-fitting. This process is not exact, so the changes are reduced by a factor of 0.7, the default value of ESTMULT=. This is to prevent changes becoming too big. But, if convergence (agreement between observed and expected scores) is happening too slowly, then higher values of ESTMULT= may be helpful.
During JMLE iterations, ESTMULT= can be changed using the Diagnosis Menu.
ESTMULT = 0.7
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the default estimation-change multiplier
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ESTMULT = 0.1 - 0.6
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changes to estimates are smaller. More iterations to convergence
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ESTMULT = 0.8 - 1.0
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changes to estimates are bigger. Perhaps fewer iterations to convergence.
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ESTMULT = 1.1 - 2.0
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changes to estimates are so big that estimates may overshoot so that estimates become worse and convergence is never reached. Change ESTMULT= when near to convergence
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Example with large dataset:
In the Estimation window on change:
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>=== ESTMULT = .778
=====================================================<
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ESTMULT= value
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JMLE MAX SCORE MAX LOGIT
ITERATION RESIDUAL* CHANGE
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Comment
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ESTMULT= 0.7
(default)
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7 -2507.00 .0008
8 -2488.50 .0007
9 -2450.00 .0007
10 -2419.00 .0007
11 -2386.00 .0007
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Slow, but safe
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ESTMULT= 1.064
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31 -1757.50 .0008
32 -1563.50 .0008
33 -1704.00 .0007
34 -1474.00 .0007
35 -1657.50 .0007
36 -1384.00 .0007
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Faster, but unstable
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ESTMULT= 0.960
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47 -1214.00 .0005
48 -1192.50 .0005
49 -1167.00 .0005
50 -1146.50 .0005
51 -1123.00 .0004
52 -1102.50 .0004
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Slow, safe
(but see below)
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ESTMULT= 1.185
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83 -773.00 .0004
84 -250.00 .0004
85 -927.00 .0004
86 21.00 .0005
87 -1232.00 .0006
88 490.00 .0007
89 -1809.00 .0009
90 1326.50 .0011
91 -2884.50 .0014
.....
104 119828.00 .0584
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Very fast, but diverges
← change ESTMULT= here
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ESTMULT= .960
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106 159415.00 .0718
107 -144812.50 -.0567
108 129760.50 .0513
109 -117978.50 -.0460
110 105562.00 .0418
111 -96084.50 -.0374
112 85834.50 .0340
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Fast, unstable, converges
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