Imagine that you want to estimate the average price of a gallon of gas in your region. You record the price of gas at 36 different gas stations (you can make these up). In your initial post, you will simply give those values, then use Excel to compute a 95% Confidence Interval for the average price. Rather than just attaching your Excel file, paste your results (or upload as an image) into the post. List all 36 gas prices in cells A1 to A36 in your excel spreadsheet. Type =average(A1:A36) to find the sample mean Type =stdev.s(A1:A36) to find the sample standard deviation Let's assume your sample mean is 3.65 with a std of 0.43. Determine the Margin of Error (for 0.05 significance) by typing =confidence.norm(.05,.43,36). This is your E value Finally, compute the 95% Confidence Interval by adding and subtracting the Margin of error from your mean: =(3.65 + E) for the Upper bound and =(3.65 - E) for the Lower bound