Fit General Linear Model - Options
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Stat > ANOVA > General Linear Model > Fit General Linear Model > Options

Use to:

·    Perform a weighted regression

·    Specify the confidence level and type of confidence interval

·    Choose the type of sum of squares

·    Perform a Box-Cox transformation on your response data when the residuals are not normally distributed or do not have constant variance

·    Display the least squares means for main effects and interaction effects in the Session window

When you transform your data, Minitab transforms the response data and uses it in the analysis. Under most conditions, it is not necessary to correct for nonnormality unless the data are highly skewed. When you use Box-Cox, all response data must be greater than 0. Check your model carefully before using the Box-Cox transformation.

Dialog box items

Weights: Enter a numeric column of weights to perform weighted regression. Weights must be greater than or equal to zero. The length of the weights column must match the length of the response column.

Confidence level for all intervals: Enter the confidence level. The default is 95.

Type of confidence interval: Choose the type of confidence interval: two-sided (default), lower bound, or upper bound.

Sums of Squares for Tests: Choose a sums of squares (SS) for calculating F and p-values. Typically, use the adjusted SS. Use sequential SS  to determine the significance of terms by the order that they enter the model.

Adjusted (Type III): Measures the reduction in the SS for each term relative to a model that contains all of the remaining terms.  

Sequential (Type I):  Measures the reduction in the SS when a term is added to a model that contains only the terms before it.

Box-Cox Transformation

No transformation: Choose to use your original response data.

Optimal l (lambda): Choose to have Minitab search for an optimal value.  

l  = 0 (natural log): Choose to use the natural log of the data.

l  = 0.5 (square root): Choose to use the square root of the data.

l : Choose to transform the data using another l value. Enter a value between -5 and 5.

Means: Use this drop-down list to quickly display the least squares means for groups of terms. If an expected term does not appear when you choose Specified terms, add it to the model. You can choose:

None

Main effects

Two-way interactions

All terms in the model

Specified terms

For more information on these options, see Displaying Means for Model Terms.

If you choose Specified terms, use the I = Calculate means for term button to identify the terms. Select a term in the list, then press the button. An I indicates that the mean of the term will be displayed.