A manufacturer claims that the mean lifetime, u, of its light bulbs is 49 months. The standard deviation of these lifetimes is 6 months. Fifteen bulbs are selected at random, and their mean lifetime...

1) Can you find two critical values (round to three decimal places)

2)

Can we conclude that the mean lifetime of light bulbs made by this manufacturer differs from 49 months?

Extracted text: A manufacturer claims that the mean lifetime, u, of its light bulbs is 49 months. The standard deviation of these lifetimes is 6 months. Fifteen bulbs are selected at random, and their mean lifetime is found to be 45 months. Assume that the population is normally distributed. Can we conclude, at the 0.05 level of significance, that the mean lifetime of light bulbs made by this manufacturer differs from 49 months? Perform a two-tailed test. Then complete the parts below. Carry your intermediate computations to three or more decimal places, and round your responses as specified below. (If necessary, consult a list of formulas.)