A manufacturer must test that his bolts are 4.00cm long when they come off the assembly line. He must recalibrate his machines if the bolts are too long or too short. After sampling 81 randomly selected bolts off the assembly line, he calculates the sample mean to be 3.97cm. He knows that the population standard deviation is 0.14cm. Assuming a level of significance of 0.01, is there sufficient evidence to show that the manufacturer needs to recalibrate the machines?

Step 1 of 4: State the null and alternative hypotheses for the test.

Step 2 of 4: Compute the value of the test statistic. Round your answer to two decimal places.

Step 3 of 4: Compute the critical value. Round your answer to two decimal places.

Step 4 of 4: Draw a conclusion and interpret the decision.