SOLUTION: Can someone let me know which formulas to use for these problems please? I have all the answers, but I want to understand how to work the problems for myself. I am studying for a f

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Question 742439: Can someone let me know which formulas to use for these problems please? I have all the answers, but I want to understand how to work the problems for myself. I am studying for a final in 5 days and would really appreciate if anyone could help me out. Thanks in advance.
Solve the problem. Round results to the nearest hundredth
A department store, on average, has daily sales of $29,539.06. The standard deviation of sales is $2,000. On Tuesday, the store sold $34,574.94 worth of goods. Find Tuesday's z score. Was Tuesday an unusually good day?

**I am doing these problems by hand, not using a calculator except for calculating figures at the end; so please do not give calculator instructions.**
Answer by Edwin McCravy(20055) (Show Source):
You can put this solution on YOUR website!
A department store, on average, has daily sales of $29,539.06. The standard deviation of sales is $2,000. On Tuesday, the store sold $34,574.94 worth of goods. Find Tuesday's z score. Was Tuesday an unusually good day?

= 2.52 That means that Tuesday's sales were 2.52 standard deviations above the mean and by the empirical rule 95% of the sales are no more than 2 standard deviations above the mean, so indeed Tuesday's sales were unually good. Edwin