Standard Scoring of surveys.

I am sure some of you math wizes can figure this out easily. I am working on a project that requires standard scoring of surveys. I have seen the formula but id like to get a step by step instruction on how to do this. Here is some example data.

http://i78.photobucket.com/albums/j1...og/problem.jpg

This table shows the scores for that question for the specific survey. The Population of the surveys, would be the number of surveys taken. My main problem is understanding where the data sets come from to calculate the mean.

Hope you guys can help me out.