Mean and standard deviation

You'll need to know if the data are normally distributed. If yes, then you want the area under the curve of the normal distribution with a Z-score greater than 1.0.

(x - mu ) / sigma , is mostly greek to me

mu and sigma are greek

OK mu is the average (100); sigma ia the stabdard deviation(15); and x is value you want (115)

Put these values in to determine z z=(x-mu)/sigma

Now go to the standard deviation table--the total area under this curve is the entire population (1), the fraction you are looking for is the area under the curve for all z greater than the z you calculate. On a standard normal population table you'll have a chart for the area under the curve less than that z. That is the fraction of the population less than that z (it will be less than 1).

But you are interedted in the fraction of the population greater than that z.

No problemo---the total value of the population is 1 (a certainity). The fraction less is given on the table for that z---so the fraction greater is 1 minus the table value (it will also be less than 1).

Check--if you get any answer that is not between zero and one you're doing something wrong.

Rap

When y'all decide to commence communicating in English, let me know. I'll come back.