posted by sayera .
a manufacturer of detergent claims that the contents of the boxes in the market weigh on average at least 16 oz.. the distribution of weights is known to be normal with a standard deviation of 0.4 oz. to test the claim of the manufacturer a random sample of 16 boxes were weighed and it was found that the sample mean weight is 15.84 oz. test at levels of significance of 5%, 10% and the null hypothesis that the population mean weight is at least 16 oz.
Z = (score-mean)/SEm
SEm = SD/√n
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions (.05 and .10) for one-tailed test related to the Z score.