![]() ![]() Selecting this option allows you to add additional charts via the form below. To access these options, select the “Revise” button on the residuals worksheet. SPC for Excel allows you to add additional charts on the Regression Charts worksheet, or to revise the regression by removing observations, removing variables, or transforming the y variables. A good model will have the points close to the line.Īdditional charts are available from the “Revise” button on the residuals worksheet. The predicted values versus observed values chart is shown below. The residuals should fall around the straight line. The normal probability plot of the raw residuals is shown below. There are two charts that are automatically created in this worksheet: a normal probability plot for the residuals and the predicted values versus observed values chart. See “Revising the Regression” below for more information. The “Revise” button on this worksheet is used to plot additional residual charts, remove observations, remove variables, or transform the y variables. The default residuals are the raw residuals, standardized residuals, internally studentized residuals, and externally studentized residuals. The residuals worksheet contains the observation number, the observed values, predicted values, and the residuals. It will also you provide 95% confidence limits for the mean at those levels, and 95% confidence limits for the predicted values. Select “Predict” and the program will predict the result. Enter levels for each predictor in the second column. The X values are listed in the first column. The last part of the summary worksheet contains the section so you can predict results. These include R Squared, adjusted R squared, the mean, standard error, coefficient of variance, the number of observations, the Durbin-Watson statistic, PRESS and the R squared prediction. The regression statistics are then given. These will be in red also if they are less than 0.05. Coefficients with p values less than 0.05 are statistically significant. This contains the coefficients, standard error, t statistic, p value, VIF, and standardized coefficient. If this is the case, the p value is shown in red. If the model is statistically significant, the p value will be less than 0.05. This is followed by the ANOVA table for the model. The regression model is shown at the top of the worksheet. This worksheet contains the data used in the regression analysis. This is necessary for the program to find the information needed to rerun the regression. The ranges containing the results on the first three sheets listed are protected. This allows you to keep track of the worksheets that go together when you remove observations, remove variables, or transform the Y variable and rerun the regression. The number in parentheses is the number of regressions in the workbook. There are four new worksheets added during the analysis: Select Cancel to exit the SPC for Excel program.Select OK to generate the regression analysis.You can change those options or add additional output such as leverage. Selecting the Options button gives the input form below.Options: contains additional residual options.Fit intercept: default is that the intercept will be fitted unchecking the box will set the intercept to 0.Enter range containing X values: the worksheet range containing the X values.Enter range containing Y values: the worksheet range containing the Y values.The ranges you selected above are the default values assuming that the Y values are in the last column. The regression input screen is shown below. Select “Regression” from the “Cause and Effect” panel on the SPC for Excel ribbon.ģ. You can use “Select Cells” in the “Utilities” panel of the SPC for Excel ribbon to quickly select the cells.Ģ. Select the shaded area (including the headings). The data must be in columns with the variable names in the first cell of the column.ġ. In this example, we are using the following model:Įnter the data into a spreadsheet as shown below. The steps below show how to do this using the SPC for Excel software. We want to use this data to determine if either factor impacts delivery time, and if we can build a model to predict delivery time. He has collected 25 observations for delivery time (minutes), the number of cases, and distance walked (feet). ![]() He decides the two factors that impact the time could be the number of cases a driver delivers, as well as how far the driver has to walk at the customer’s facility. An engineer employed by a soft drink beverage bottler is analyzing what impacts delivery times. We will use an example from Montgomery’s regression book. This page shows how to perform multiple linear regression using SPC for Excel. ![]()
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