S = Standard Deviation
Ý = Sum of
= each data point in a data set
mean = the average of the data points
N = the number of data points.
To calculate S.D., look at your final graph of averaged data. What is your DV & IV on the graph? If it is reaction rate, then you must calculate the reaction rate for each of the trials at each concentration as in the table seen below. If you are calculating change in mass (DV) vs. concentration or drink, you would calculate the change for each of the trials of each concentration or drink. If it is change in volume, or change in length,you would do the same thing. If it is the percent change in mass/volume/ or length, you would do the same thing!
Notice that the standard deviation is calculated using the separate trial reaction rates plus the average reaction rate for each concentration in the example above! You can set it up like this for each of your individual labs using Microsoft Excel. Obviously, the labels, units and title will vary with each experiment!
[How to Use Standard Deviation to Compare Data Sets]
[Reporting Mean Data Using Standard Deviation Calculations]