• The sum of all the data points divided by the number of data points.

• Measure of central tendency for normally distributed data.

• DO NOT calculate a mean from values that are already averages.

• DO NOT calculate a mean when the measurement scale is not linear (i.e. pH units are not measured on a linear scale)

Calculating the Mean in Microsoft Excel

Open Excel and enter your data in columns. You can label the columns if you prefer. To calculate mean:

• Click on the box in which you want the mean to be placed

• Click the "Formulas" tab at the top of the screen

• Select the “Insert Function button”

• A new box pops up. Search to find the AVERAGE option, click OK

• Highlight the data of which you want the average to be calculated, click OK

• Be sure your mean has the correct number of digits. Your processed data should have the same number of digits as your raw data. So, in the example, the mean should be a whole number. To do this, click the box which is displaying the mean and on the "Home" tab click the decrease decimal button until you have the correct number of digits showing.