Homework Help: Math Quantitive Reasoning

Posted by Lindsey on Sunday, December 2, 2007 at 8:32pm.

The amount of Jen's monthly phone bill is normally distributed with a mean of $50 and a standard deviation of $12. What percentage of her phone bills are between $14 and $86?

Math Quantitive Reasoning - Reiny, Sunday, December 2, 2007 at 8:56pm
the z score for $14 is (14-50)/12 = -3
the z score for $86 = (86-50)/12 = +3

at this point you will need a table of values of z scores, or some distribution calculator
Here is a rather simple one

http://davidmlane.com/hyperstat/z_table.html

You could either enter
mean: 0
standard deviation: 1
between -3 and +3

or for this one we didn't even have to calculate the z-scores and could have entered
Mean 50
SD 12
between 14 and 86, notice we got the same result, .9973 which is 99.73%

Answer this Question

Related Questions

Math - Use the 68-95-99.7 rule to solve the problem. - The amount of Jen's ...
Statistics - The amount of a monthly phone bill is normally distributed with a ...
mathematical modeling - Use the 68-95-99.7 rule to solve: The amount of Jen'...
Word Problem - A math teacher gives two different tests to measure students'...
Math - According to a student project for statistics 250, the amount of money ...
Math please help! - According to a student project for statistics 250, the ...
Math - Random variables X and Y are both normally distributed with mean 100 and ...
statistics - The average electric bill in a residential area is $72 for the ...
Math - According to CTIA-The Wireless Association, the mean monthly cell phone ...
Stats - a plumbing supplier's mean monthly demand for vinyl washers is 24212...

For Further Reading

First Name:
School Subject:
Answer: