This week on It Figures… our graph discussion continues! When putting your data sets together, it is important to think about error bars for your graphs. A lot of programs will (very easily, actually!) calculate these values for you, so be sure to include them. You can choose either Standard Error of Mean (SEM) or Standard Deviation (SD). Both important, but both different:
SEM = is the relationship between the dispersion of individual observations around the population mean (the standard deviation), and the dispersion of sample means around the population mean (the standard error)1
SD = is used to quantify the amount of variation or dispersion of a set of data values2
Yes, I did pull those definitions off of Wiki, but there is no need to reinvent the wheel. I cannot stress how important it is to put error bars on your graphs – Just do it!