Standard Error of Mean 

Standard Error of the Mean

What Is It?

Standard error of the mean is kind of similar to standard deviation in that they can represent how confident we are in the data. Basically, the standard error of the mean estimates the variability between sample means that you would get if you took several samples from the data set.The standard error of the mean can be represented with standard error bars, which are visually shown on a graph. The size of the standard error bars says a lot. If I have lots of data in my sample, I will feel more confident, and thus the standard error bars will be smaller.

Standard error bars will look a few different ways depending on the data, but you will often see them in scatterplots (left) and bar graphs (right). Basically, the point (on the scatterplot) or the top of the bar (on the bar graph) represent the data that was collected, but the standard error bars basically show a range of data that would be unsurprising to see in the circumstances. So the smaller the error bars, the more confident we are in the data represented by the scatterplot or bar graph.

How to Use Your Calculated Standard Error

Now that you have your standard error of the mean, you simply multiply it by 2. Now add and subtract 2*Standard error of the mean (SEM) [mean +/- 2SEM]. Those values are what you mark for your standard error bars.

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