of the test.The mean of the pressure required to open a certain valve is known to be u = 6.6 psi. Due to changes in the manufacturing process, the quality-control

manager feels that the average pressure hypothesis was rejected. O A. There is sufficient evidence that the mean of the pressure required to open a certain valve has increased. O B. There is sufficient evidence that the mean of the pressure required to open a certain valve has not changed. OC. There is not sufficient evidence that the mean of the pressure required to open a certain valve has increased. O D. The mean of the pressure has not changed. DE. The mean of the pressure has increased. O F. There is not sufficient evidence that the mean of the pressure required to open a certain valve has not changed.