Solution:
Given:
From the data, sample mean is
= 9.20 and the Sample standard
deviation is s = 0.21
The sample size is n = 50.
a) Null and Alternative Hypotheses:

This corresponds to a left-tail test, for which a t-test for one mean, with unknown population standard deviation will be used.
Test statistic:

The number of degrees of freedom are df = n-1 = 50-1 = 49
Rejection Region:
Given significance level = α = 0.05 and df = 49
So Critical Value for the test is, tc = -1.677 …Using
excel formula, =TINV(2*(1-0.05),49)
Decision:
Since it is observed that |t| =
6.734> |tc| = 1.677
It is then concluded that the Null Hypothesis is
rejected.
b) Conclusion: There is not enough evidence to conclude that the process by which the insulator are manufactured is equivalent to the standard.
Done
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