In a manufacturing process a random sample of 9 bolts manufactured has a mean length of 3cm with a variance of 0.09.Assuming bolt length is normally distributed,what is the 90% confidence interval for the true mean length of the bolt?
A)2.8355 to 3.1645
B)2.5065 to 3.4935
C)2.4420 to 3.5580
D)2.8140 to 3.8160
E)2.9442 to 3.0558

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The Answer of In a manufacturing process a random sample of 9 bolts manufactured has a mean length of 3cm with a variance of 0.09.Assuming bolt length is normally distributed,what is the 90% confidence interval for the true mean length of the bolt?
A)2.8355 to 3.1645
B)2.5065 to 3.4935
C)2.4420 to 3.5580
D)2.8140 to 3.8160
E)2.9442 to 3.0558

In a Manufacturing Process a Random Sample of 9 Bolts