Consumer Research • Item Analysis • Launch the Item Analysis Platform
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Launch the Item Analysis Platform
Launch the Item Analysis platform by selecting Analyze > Consumer Research > Item Analysis.
Item Analysis Launch Window
Y, Test Items
Assigns two or more columns to be analyzed. The columns must be numeric, continuous, and contain only 0s and 1s.
Tip: Use Cols > Recode if you need to recode your data to 0s and 1s. See Recode Valuesin the Discovering JMP book.
Freq
Assigns a frequency variable to this role. This is useful if your data are summarized.
By
Produces a separate report for each level of the By variable. If more than one By variable is assigned, a separate report is produced for each possible combination of the levels of the By variable.
Model
Specifies the desired model from the following options:
Logistic 2PL
The 2-parameter logistic model.
Logistic 3PL
The 3-parameter logistic model.
Logistic 1PL
The 1-parameter logistic model with a Rasch parameterization.
Logistic 3PL Model Details
If you select Logistic 3PL for Model, you are prompted to enter a penalty for the guessing parameters after you click OK. For a 3PL model, the default value of the penalty is zero. However, you can enter a non-zero penalty for the c parameters (the guessing for each item). This penalty is similar to the type of penalty parameter that you would use in ridge regression. The penalty is on the variance of the estimated guessing parameters. The use of the penalty has the following benefits:
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Stabilizes the estimation of model parameters.
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Speeds up computations.
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Reduces the variability of the guessing parameter across items at the expense of some bias.
Large values of the penalty force the guessing parameters to zero while smaller values help reduce the variability of the guessing parameter across items. A value of zero can be used for no penalty.

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Help created on 9/19/2017