Use a service bill of the last 12 months (electric bill, cell phone bill, water bill, etc). If you don't feel like using a real bill, you can make up values.

i. List the values of your bill for the last 12 months on one column

ii. Find the sample mean and sample standard deviation of your data

iii. Pick 3 bills from the last 12 months and change the values into z-scores. What does the z-score tell you about that particular month ?

Analysis

i. Between what two values would be considered a normal bill ? Remember, being within

2 Standard Deviations is considered normal .

ii. Are any of your bills in the last 12 months unusual ? Very unusual ?

iii. Are there times when you would accept an "unusual" bill ? Explain.