A materials engineer at a furniture manufacturing site wants to assess the stiffness of the particle board that the manufacturer uses. The engineer measures the stiffness and the density of a sample of particle board pieces.
The engineer uses simple regression to determine whether the density of the particles is associated with the stiffness of the board.
On the Options tab, select Display 95% confidence interval and Display 95% prediction interval.
On the Graphs tab, select Residual plots.
Interpret the results
The p-value for density is less than 0.0001, which is less than the significance level of 0.05. These results indicate that the association between stiffness and density is statistically significant. However, there appears to be an outlier in the top right corner of the fitted line plot. This point corresponds to observation 21, which is shown in the table of Fits and Diagnostics for Unusual Observations. Because the outlier could have a strong effect on the results, the engineer should investigate this point to determine its cause.