State the conclusion based on the results of the test. the mean of the pressure required to open a certain valve is known to be mu equals 8.4 psi. due to changes in the manufacturing process, the quality-control manager feels that the average pressure has increased. the null hypothesis was rejected. choose the correct answer below.
a. there is not sufficient evidence that the mean of the pressure required to open a certain valve has not changed.
b. there is not sufficient evidence that the mean of the pressure required to open a certain valve has increased.
c. the mean of the pressure has not changed.
d. the mean of the pressure has increased.
e. there is sufficient evidence that the mean of the pressure required to open a certain valve has increased.
f. there is sufficient evidence that the mean of the pressure required to open a certain valve has not changed.