Signal/Noise ratio question.

Hello folks, I went through the forum rules, so I hope this would be the right place for my topic. I have a few (two) questions regarding the calculation of the signal to noise ratio for a unipolar binary signalling system. Here is the assignment:

“A unipolar binary signalling system is to be employed over a noisy channel. The channel noise voltage, amplitude is 50mV/Div. In order to quantify the noise signal 250 points were sampled and recorded within a 100mS time period the results of which are given in a Microsoft Excel spreadsheet.

Determine the noise power of the channel and calculate, for signal amplitudes of 0.1 and 0.5 volts, the signal to noise ratio and hence the bit error probability.”

So my questions are:
1. I`m not sure why exactly do I need the spreadsheet, what to do with the data from it (the time vs. voltage chart), hence I`m not quite sure how to determine the noise power for the channel.
2. When I use the error probability formula I`m getting a very high error probability something like 399bits per 1000 bits.

Any help would be greatly appreciated. Thank you very much for your time.😀