# Perform a linear regression analysis

Perform a linear regression analysis### Minitab Procedures

- Select
**Stat**>>**Regression**>>**Regression**>>**Fit Regression Model ...** - Specify the response and the predictor(s).
- (For standard residual plots) Under
**Graphs**..., select the desired residual plots. - Minitab automatically recognizes replicates of data and produces Lack of Fit test with Pure error by default.
- Select
**OK**.

Next, back up to the Main Menu having just run this regression:

- (To get a prediction interval) Select
**Stat**>>**Regression**>>**Regression**>>**Predict**... - Specify the response.
- Specify either the x value ("
**Enter individual values**") or a column name ("**Enter columns of values**") containing multiple x values. - Select
**Options**... Specify the**Confidence level**— the default is 95%. Select**OK**. - Select
**OK**. The output will be displayed in the session window.

### Regression Through the Origin

To fit an RTO model click "**Model**" and uncheck "Include the constant term in the model".

### Example

The iqsize.txt data set contains data on the IQ (*y* = *PIQ*), brain size (*x*_{1} = *Brain*), height (*x*_{2} = *Height*), and weight (*x*_{3} = *Weight*) of *n* = 38 college students. Fit the multiple linear regression model treating *PIQ* as the response, and *Brain*, *Height*, and *Weight* as the predictors. In doing so, request a lack of fit test. Also, with 95% confidence, predict the *PIQ* of a randomly selected college student whose *Brain* = 90, *Height* = 70 and *Weight* = 150.

**Minitab Dialog Boxes**

**Resulting Minitab Output**