Can we use iNZight to work out residuals and draw residual plots? (3.9)
I guess you are talking about residual plots for linear regression in which case you will have to form the residuals 鈥渂y hand鈥 using the Manipulate Variables menu
Suppose that you were predicting height from age:
- Drag variable names to produce the height vs age聽 scatter plot
- Use Add to Plot to put a linear trend on it
- Click Get Summary (or Get Inference) to obtain the intercept and slope from the fitted line. Suppose it turns out:聽 int=96.71 slope = 4.83
- Use 鈥淐reate New Variables鈥 which is under 鈥淢anipulate Variables鈥.
- For understandability I鈥檇 do it in 2 steps 鈥
a.聽 Create PredHeight = 96.71 + 4.83*age
b.聽 Create Resids = height 鈥 PredHeight
Then you can plot Resids against anything you like聽 (in iNZight all variable names are case sensitive)
I didn鈥檛 get this 鈥渃anned鈥 in the basic part of iNZight because in a bivariate setting (a single predictor variable) you seldom see anything in a residual plot you can鈥檛 see in the original scatter plot so I would not stress residual plots in a first bite at regression (except maybe for your brighter students).
If you turn them loose on the Model Fitting module under 鈥淎dvanced鈥 then residual plots are generated automatically but that part was really designed for university courses.
