Question 324664: To test the null hypothesis that the average lifetime for a particular brand of bulb is 775 hours versus the alternative that the average lifetime is different from 775 hours, a sample of 120 bulbs is used. If the standard deviation is 65 hours and α is equal to 0.01, what values for xbar will result in rejection of the null hypothesis (show all work).
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! To test the null hypothesis that the average lifetime for a particular brand of bulb is 775 hours versus the alternative that the average lifetime is different from 775 hours, a sample of 120 bulbs is used. If the standard deviation is 65 hours and α is equal to 0.01, what values for xbar will result in rejection of the null hypothesis.
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Ho: u = 775
Ha: u is not 775
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Critical value for 2-tail t-test with alpha=1% and df=119 = +-2.6178
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xbar = 2.6178*65+775 = 945.16
or
xbar = -2.6178*65+775 = 604.84
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Any xbar< 604.84 or greater than 945.16 will result in rejection of Ho.
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Cheers,
Stan H.
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