Z = (mean1 - mean2)/standard error (SE) of difference between means
SEdiff = √(SEmean1^2 + SEmean2^2)
SEm = SD/√n
If only one SD is provided, you can use just that to determine SEdiff.
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score. As a percentage, is it more or less than 1%?
A large furniture store has begun a new ad campaign on local television. Before the campaign, the long term mean daily sales were $24,819. A random sample of 40 days during the new ad campaign gave a sample mean daily sale of $25,910. Does this indicate that the population mean daily sales is now more than $24,819? Use a 1% level of significance. Assume o = $1,917.
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