From the point of view of the city, the strength of a supplier's pipe is assumed to be less than its requirements until proven otherwise. Find the corresponding to the significance level. Finally, we find the area of the acceptance region under the alternate distribution. This area is .7764. If the sample mean had been 2450 instead of 2425, would have been .4522 and the power would have increased to .5478.
Power increases as the distance between the null and sample means increases.
He wants to find out if this represents a significant departure from the the old powder. This is a two-tailed test, since if isn't equal to 1.2, it is either greater than 1.2 or less than 1.2. As before, find the values of corresponding to the critical values. Remember, these are the values of that support H0. As alpha is decreased, so is the power of the test.