Calculate a partial correlation coefficient

Suppose you want to calculate the partial correlation between catalyst ratio and rating of wrinkle resistance, removing the effect of formaldehyde concentration:

Regress rating on formaldehyde concentration and store the residuals.
1. Open the Minitab sample data set WrinkleResistance.MTW.
2. Choose Stat > Regression > Regression > Fit Regression Model.
3. In Responses, enter Rating. In Continuous predictors, enter Conc.
4. Click Storage, and check Residuals. Click OK in each dialog box.
Regress catalyst ratio on formaldehyde concentration and store the residuals.
1. Choose Stat > Regression > Regression > Fit Regression Model.
2. In Responses, enter Ratio. In Continuous predictors, enter Conc.
3. Click OK.
Calculate the correlation coefficient for the two columns of residuals.
1. Choose Stat > Basic Statistics > Correlation.
2. In Variables, enter RESI1 and RESI2. Click OK.
The result is 0.765, which indicates that a strong linear relationship remains between catalyst ratio and rating of wrinkle resistance after the linear relationships between these variables and formaldehyde concentration have been removed.