SOLUTION: A manufacturer of a certain type of auto batteries claims that the mean life of batteries is 45 months. A consumer protection agency that wants to check the claim took a random sam

Question 871995: A manufacturer of a certain type of auto batteries claims that the mean life of batteries is 45 months. A consumer protection agency that wants to check the claim took a random sample 36 such batteries and found that the mean life for the sample is 43.75 months, with a standard deviation of 4 months.
a) Using the 2.5% significance level, would you conclude that the mean life is less 45 months.
b) Using the 5% significance level, would you conclude that the mean life of the batteries is less 45 months

Thank you in advance!!!
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!
Ho: u = 45 (claim)
Ha: u < 45
t = -1.25/4/sqrt(36) = -1.875
P(t < 1.874) = .0346 0r 3.46% DF(35)
a) Using the 2.5% significance level, would you conclude
that the mean life is less 45 months. NO. 3.46% is not less than 2.5%
b) Using the 5% significance level, would you conclude
that the mean life of the batteries is less 45 months? YES. 3.46% < 5%
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