Starbucks Coffee Co. uses a data-based approach for improving the quality and customer satisfaction of its products. When survey data indicated that Starbucks needed to improve its package sealing process, an experiment was conducted (data extracted from L. Johnson and S. Burrows, "For Starbucks, It's in the Bag," Quality Progress, March 2011, pp. 17-23) to determine the factors in the bag-sealing equipment that might be affecting the ease of opening the bag without tearing the inner liner of the bag. Among the factors that could affect the rating of the ability of the bag to resist tears were the viscosity, pressure, and plate gap on the bagsealing equipment. Data were collected on 19 bags in which the plate gap was varied. The results are stored in Starbucks .
a. Using all the data as the training sample, develop a regression tree model to predict the rating of the ability of the bag to resist tears.
b. What conclusions can you reach about the rating of the ability of the bag to resist tears?