Question 279758
 A manufacturer receives an order for fluorscent light bulbs. 
The order requires that the bulbs have a mean life span of 550 hours. 
The manufacturer selects a random sample of 25 fluorescent light bulbs and finds that they have a mean life span of 545 hours with a standard deviation of 15 hours. Is the manufacturer making acceptable light bulbs? Defend your answer. use a 95% confidence level. Assume the data is normally distributed.
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sample mean = 545
standard error = E = invT(0.975.24)*15/sqrt(25) = 6.1917
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95% CI: 545-6.1917 < u < 545+6.1917
95% CI: 538.81 < u < 551.19
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Cheers,
Stan H.