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# Overdue Bills Following a Normal Curve & Determining Likely Voters

6. A large population of overdue bills has balances that follow a normal curve. When we take a sample of 100 of these the average is \$500 and the SD is \$100.
(a) What statement can you make about the range \$300 to \$700?
(b) What statement can you make about the range \$480 to \$520?

10. Pollsters try to determine whether or not a person is a 'likely voter' before they count their opinion in a poll. If we assume 40% of the registered voters will actually vote, in a random sample of 100 registered voters we can be 95% confident that somewhere between ________ and ________ of them will actually vote. Fill in the blanks with a number.

Please show your work so I can see what you did and help me better understand.

#### Solution Preview

6.
a) Based on the Rule of Thumb (alternatively known as the 68-95-99.7 rule), we know that 95% of the values lie between +/- 2 standard deviations of the mean for a normal distribution. Since our standard deviation is \$100 and our mean is \$500, +/- 2 standard deviations translates to the exact range we are asked about. We can thus say that on average, we would expect 95 ...

#### Solution Summary

The solution is 261 words of explained calculations on how to answer these normal curve and range questions.

\$2.19