1. ## Quartiles/Normal Distribution

I have a test tomorrow and I'm working on a practice problem right now that I can't see to understand. Please help!

The amount of Jen's monthly phone bill is normally distributed with a mean of $76 and a standard deviation of$12. Find the first quartile,

I understand that the mean goes in the middle of the bell curve, and the SD is the intervals between the other numbers on the curve. But how do I get that ?

If it helps, the answer is $67.96. 2. Originally Posted by juicysharpie I accidentally placed this question under the other statistics section. Sorry if it confused anyone. Here we go again... I have a test tomorrow and I'm working on a practice problem right now that I can't see to understand. Please help! The amount of Jen's monthly phone bill is normally distributed with a mean of$76 and a standard deviation of $12. Find the first quartile, I understand that the mean goes in the middle of the bell curve, and the SD is the intervals between the other numbers on the curve. But how do I get that ? If it helps, the answer is$67.96.
The first quartile is the value that is exceeded with probability 0.75, or is not exceeded with probability 0.25. You look this up in a table of the standard normal distribution to give the z-score corresponding to the quartile (~=-0.674) and convert that to a bill in the usual way.

CB