Stability Study
Model Selection
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Stability StudyModel Selection |
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If your data include a batch factor, then the model selection table shows the results of the model selection process. Minitab uses the final model from the selection process to estimate shelf life.
Minitab starts with the full model that includes time, batch, and the batch by time interaction. Minitab then compares the p-value for the interaction to the value specified in Alpha for pooling batches (also called a). If the p-value for the interaction is less than a, then the model cannot be reduced. The final model includes all three terms.
If the p-value for the interaction is greater than or equal to a, then Minitab removes the interaction and evaluates the reduced model with only time and batch. If the p-value for batch in the reduced model is less than a, then the model cannot be reduced further. The final model includes time and batch.
If the p-value for batch in the reduced model is greater than or equal to a, then Minitab removes batch. The final model includes only time.
Example Output |
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Model Selection with α = 0.25
Source DF Seq SS Seq MS F-Value P-Value Month 1 122.460 122.460 345.93 0.000 Batch 4 2.587 0.647 1.83 0.150 Month*Batch 4 3.850 0.962 2.72 0.048 Error 30 10.620 0.354 Total 39 139.516
Terms in selected model: Month, Batch, Month*Batch |
Interpretation |
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For the pill data, the p-value for the Month by Batch interaction (Month*Batch) is 0.048. Because the p-value is less than the a-level of 0.25, the model cannot be reduced.
