# Minitab Help 10: Model Building

Minitab Help 10: Model Building

## Martians (underspecified model)

• Perform a linear regression analysis of weight vs height + water. Click "Storage" and select "Fits" before clicking "OK."
• Select Calc > Calculator, type "FITS0" in the box labeled "Store results in variable," type "if(water=0, FITS)" in the box labeled "Expression," and click "OK." Repeat to create "FITS10" as "if(water=10,FITS)" and "FITS20" as "if(water=20,FITS)."
• Perform a linear regression analysis of weight vs height (an underspecified model). Click "Storage" and select "Fits" before clicking "OK." The resulting variable should be called "FITS_1."
• Create a basic scatterplot but select "With Groups" instead of "Simple." Plot "weight" vs "height" with "water" as the "Categorical variable for grouping."
• To add parallel regression lines representing the different levels of water to the scatterplot, select the scatterplot, select Editor > Add > Calculated Line, and select "FITS0" for the "Y column" and "height" for the "X column." Repeat to add the "FITS10" and "FITS20" lines.
• To add a regression line representing the underspecified model to the scatterplot, select the scatterplot, select Editor > Add > Calculated Line, and select "FITS_1" for the "Y column" and "height" for the "X column."

## Measurements of college students (variable selection using stepwise regression)

• Conduct stepwise regression for Height vs LeftArm + LeftFoot + LeftHand + HeadCirc + nose + Gender.
• Change the "Method" to "Backward elimination" or "Forward selection."

 [1] Link ↥ Has Tooltip/Popover Toggleable Visibility