Stored Model Overview
overview  

Minitab automatically stores the last model that you fit for many of the linear model analyses. You can use these models to quickly and easily create graphs, make predictions, and optimize responses. Minitab automatically saves the following types of models:

·    Factorial Designs

·    General Full Factorial Designs

·    Analyze Variability

·    Response Surface Designs

·    General Linear Models (GLM)

·    Regression

·    Binary Logistic Regression

·    Poisson Regression

After Minitab stores a model, you can use the following analyses. These analyses become active when the active worksheet contains a stored model that satisfies the minimum requirements.

 

Analysis

  

Purpose

Minimum requirements

Predict

To predict the value of the response variable (fitted values) for the combinations of variable settings that you request

Any number and type of variables

Factorial Plots

To visualize the main effects and interaction effects

Any number and type of variables (except GLM, which requires categorical variables)

Contour Plot

To show how the fitted response relates to two continuous variables with a two-dimensional view

Two or more continuous variables

Surface Plot

To show how the fitted response relates to two continuous variables with a three-dimensional surface

Two or more continuous variables

Cube Plot

To see the factors and combination of settings used in your design

A 2-level factorial design

Overlaid Contour Plot

To display contour plots for multiple responses in a single graph  to visually identify an area where all of the responses are in a desirable range

Two or more continuous variables

Response Optimizer

To identify the combination of input variable settings that jointly optimize a single response or a set of responses

Any number and type of variables

Model Details

The output from these analyses are accurate only if you use the correct model. Minitab stores the most recent model for a response variable each time you run the analysis. Any model that you previously fit for that response variable is overwritten. To help ensure that the currently stored model is the correct model, Minitab provides several ways for you to view the model information. Use your knowledge of the analysis' history to determine whether the current model is the correct model.

Data Window

After you fit a model for a response variable, an indicator appears in the bottom right corner of the column heading on the worksheet. A green indicator tells you that the model is up-to-date while a red indicator signifies an out-of-date model. A model is out-of-date when the data have changed since you fit the model. If you hover the pointer over the indicator, a tool tip appears that provides information about the model.

View Model dialog box

Each model-based analyses has a View Model button that you can click before you use the analysis. You can examine all of the models of the same type  that are stored in the worksheet. You can only use an analysis if the model is both up-to-date and satisfies the minimum requirements.

Additionally, after you create a graph, you can right click the graph and choose View Model Used for Graph in the context menu that appears. A graph is out-of-date when the model, data, or worksheet change since you created the graph. The context menu is an easy way to see which model created the graph and why the graph is not current.