Analysis of an Experiment with Two- and Three-Level Factors - Residual Plots Tab
Designs for Factors at 2 and 3 Levels
Select the Residual plots tab of the Analysis of an Experiment with Two- and Three-Level Factors dialog to access options to generate various diagnostic plots of the raw residuals and/or the studentized deleted residuals. These results are for the currently specified model. You can specify a new model on the Model tab. Note that for plots involving residuals, either the raw residual values or the studentized deleted residuals will be used depending on whether the Plot raw residuals or the Plot studentized deleted residuals option button is selected.
- Plot raw residuals
- If the Plot raw residuals option button is selected, residual plots will use the raw residuals on the dependent variable for each case or run as the values to be plotted.
- Plot studentized deleted residuals
- If the Plot studentized deleted residuals option button is selected, residual plots will use the studentized deleted residuals on the dependent variable for each case or run as the values to be plotted.
- Histograms
- Use the options in the Histograms group box to plot either a histogram of residuals or a histogram of predicted values.
- Histogram of residuals
- Click the Histogram of residuals button to display a Histogram of Raw Residuals showing the frequency distribution, given the current model, of the selected residuals (raw or studentized deleted) for the dependent variable. The ANOVA analysis assumes that the residual values follow the normal distribution. Note that this plot also shows the fitted normal distribution curve.
- Histogram of predicted values
- Click the Histogram of predicted values button to display a Histogram of Predicted Values, given the current model, showing the frequency distribution of the predicted values for the dependent variable. Note that this plot also shows the fitted normal distribution curve.
- Probability plots of residuals
- Three probability plots of residuals are available in the Probability plots of residuals group box: Normal, Half-normal and Detrended normal.
- Normal plot
- Click the Normal plot button to display a Normal Probability Plot of the Residuals, which plots the Expected Normal Values and corresponding probabilities against the selected residual (raw or studentized deleted) values of the dependent variable for each case or run.
The so-called normal probability plot is a common tool to assess how closely a set of observed values (residuals in this case) follows a theoretical distribution. In this plot the actual residual values are plotted along the horizontal x-axis; the vertical y-axis shows the expected normal values for the respective values, after they were rank-ordered. If all values fall onto a straight line you can be satisfied that the residuals follow the normal distribution.
- Half-normal Plot
- Click the Half-normal plot button to display a Half-Normal Probability Plot of the Residuals, which plots the Expected Half-Normal Values and corresponding probabilities against the selected residual (raw or studentized deleted) values of the dependent variable for each case or run.
- Detrended normal plot
- Click the Detrended normal plot button to display a Detrended Normal Probability Plot of the Residuals, which plots the Deviations from Expected values against the selected residual (raw or studentized deleted) values of the dependent variable for each case or run.
- Scatterplots
- Five scatterplots are available in the Scatterplots group box: Predicted vs. residual values, Observed vs. predicted values, Observed vs. residual values, Residuals vs. deleted residuals, and Residuals vs. case numbers.
- Predicted vs. residual values.
- Click the Predicted vs. residual values button to display a Predicted vs. Residual Values Plot, which plots the selected residual values (raw or studentized deleted) against the Predicted Values of the dependent variable for each case or run.
- Observed vs. predicted values.
- Click the Observed vs. predicted values button to display an Observed vs. Predicted Values Plot, which plots the Observed Values against the Predicted Values of the dependent variable for each case or run.
- Observed vs. residual values.
- Click the Observed vs. residual values button to display an Observed vs. Residual Values Plot, which plots the selected residual values (raw or studentized deleted) against the Observed Values of the dependent variable for each case or run.
- Residuals vs. deleted residuals.
- Click the Residuals vs. deleted values button to display a Residuals vs. Deleted Residuals Plot, which plots the Studentized Deleted Residuals against the Raw Residuals of the dependent variable for each case or run.
- Residuals vs. case numbers.
- Click the Residuals vs. case numbers button to display a Residuals vs. Case Numbers Plot, which plots the selected residual values (raw or studentized deleted) against the Case numbers for each case or run.