You should apply error analysis in the ways that you know how. If you forget the relevant ways, you should use my processes which are outlined below. Feel free to check with me on clarification of error analysis.

Background:

90% confidence interval: http://physics.randolphcollege.edu/lab/105_1115lab/stats/Default.html starting in the middle of the page at: "Given a set of numbers which..."

combining errors: http://physics.randolphcollege.edu/lab/105_1115lab/motion_error/Default.html click on combining errors in the menu, read the top section, and skip to the section labeled "Physics 1115"

straight line fit: same link as above, and click on straight line fit in the menu

Relevant Excel Commands:

For curve fitting, you can use Excel or anything else. If you know how, I strongly advise that you use some scientific analysis program like Matlab or Mathcad, but we are not going to focus on that in this class.

For curve fitting and error analysis in Excel: http://physics.randolphcollege.edu/lab/IntroLab/Reference/exchint.html. You are going to need linest, trendlines, and/or regression when you do striaght line fitting, or basic exponential and polynomials. You will need solver when you do more complicated curve fitting.