SOLUTION: The new Twinkle bulb has a standard deviation 34 hours. A random sample of 77 light bulbs is selected from inventory. The sample mean was found to be 492 hours. Find the margin of

Question 221674: The new Twinkle bulb has a standard deviation 34 hours. A random sample of 77 light bulbs is selected from inventory. The sample mean was found to be 492 hours. Find the margin of error E for a 90% confidence interval. Round your answer to the nearest hundredths. Then I have to construct a 90% confidence interval for the mean life. I know how to do that part I just can't figure out the first part. The sqrt gets me.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The new Twinkle bulb has a standard deviation 34 hours.
A random sample of 77 light bulbs is selected from inventory.
The sample mean was found to be 492 hours.
Find the margin of error E for a 90% confidence interval. Round your answer to the nearest hundredths.
Then I have to construct a 90% confidence interval for the mean life.
I know how to do that part I just can't figure out the first part. The sqrt gets me.
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invT(0.05,76) = -1.6652
------------
E = 1.6652[34/sqrt(77)] = 6.4519
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90% CI: 492 - 6.4519 < u < 492 + 6.4519
=================================================
Cheers,
Stan H.
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