[Blindmath] Statistics help

[Sabra Ewing]

I need help with this statistics problem because I don't have access to many of the formulas  in my class. I tried to work with a group, but they haven't been very nice. They have just said that we went over it in class, when I can't understand what my professor writes on the board, and have received very little material in an accessible format. Anyways, here's the problem.

A large number of voltages show a mean of 118.5V and a population standard deviation of 1.20V. Determine the percentage of data that falls between 116 and 120 Volts. If it is desired to have 12.1% of the voltage below 115V, how should the mean voltage be adjusted? The dispersion is σ = 1.20 V.

I know it has something to do with the empirical rule, but I don't know what to do because it doesn't fall an even number of standard deviations from the mean. For the second part of the problem, I have no idea what to do.




          




Sabra Ewing