Starbucks Coffee Co. uses a data based approach to 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 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. (Data extracted from L. Johnson and S. Burrows, “For Starbucks, It’s in the Bag,” Quality Progress, March 2011, pp. 17– 23.) One factor that could affect the rating of the ability of the bag to resist tears was the plate gap on the bag sealing equipment. Data were collected on 19 bags in which the plate gap was varied. The results are stored in Starbucks.
a. Construct a scatter plot.
b. Assuming a linear relationship, use the least squares method to determine the regression coefficients b0 and b1.
c. Interpret the meaning of the slope, b1, in this problem.
d. Predict the mean tear rating when the plate gap is equal to 0. e. What should you tell management of Starbucks about the relationship between the plate gap and the tear rating?