I came across an example where standard deviation was being plotted on a Cartesian plot (standard 2D with X and Y axes.)
This seems like a valid thing to do but in this case the example only had a single line running across the graph to "indicate" standard deviation. This to me seems not very useful, possibly dangerous and misleading. Don't you need three lines plotted to properly visualize standard deviation on a graph? Thusly:
- The mean
- The mean plus one standard deviation value
- The mean minus one standard deviation value
P.S. I am a software developer working on a data visualization package so please take my use of stats terminology with a grain of salt. Any corrections and feedback will be sincerely appreciated.
Rephrasing the question:
If I had a set of five data points to plot on a cartesian plane:
X: 10 20 30 35 50 Y: 20 40 5 55 10
For this sample data set (the Y values) the mean is 20 and the stdev is ~21.036 (x values plotted along the X axis and y values plotted along the Y axis.)
What would a proper plotting of the mean and the stdev on top of the X/Y data set look like?