Question

State the conclusion based on the results of the test. The standard deviationstandard deviation inin the pressure required to open a certain valve is known to be sigma equals 1.3 psi.σ=1.3 psi. Due to changes in the manufacturing​ process, the​ quality-control manager feels that the pressurepressure variabilityvariability has changedchanged. 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 sufficient evidence that the mean of the pressure required to open a certain valve has changed. C. The mean of the pressure has not changed. D. The mean of the pressure has changed. E. There is sufficient evidence that the mean of the pressure required to open a certain valve has not changed. F. There is not sufficient evidence that the mean of the pressure required to open a certain valve has changed.

Answer 1

B. There is sufficient evidence that the mean of the pressure required to open a certain valve has changed.

Explanation:

We make this conclusion based on these reasons:

1. We are told that the "null hypothesis was rejected" after the "manager feels that the pressure variability has changed., meaning the null hypothesis was the opposite of what occurred; that is to say, it is the alternate hypothesis that proved true instead.
2. "changes in the manufacturing​ process" form what can be called "sufficient evidence" that the mean of the pressure required to open the valve has changed, thereby going against the null hypothesis.

It is based on the above reasons that the null hypothesis was rejected.