Statistics (Math) Homework Check

This project is of an academic nature. It requires current high level knowledge (2nd year college / university) of math and statistics. I need explanation of basic Statistic formulas and a double check of work attached. Need to know where I went wrong, you can modify the scans with any photo editing software and post back. Lastly, please see my profile (I'm originally from [login to view URL]) at http://www.freelancer.com/u/racerx92.html, I have 15+ projects posted and paid for, I have 5 star rating on all but one project (4.6 overall). I tend to work with a single worker for about a 3 or 4 month period (I've previously worked with coderforrental, voker57, vano101,derley) I tend to give bonuses to great work. I'm looking to continue working a single worker for the next 4 months (for Statistics / Calculus academic type work), keep this in mind. Please feel free to ask questions, and offer suggestive bids. I'll post sample of required work within the hour of this post.