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Graphing a data set with standard deviations?

A

astroview

Golden Member
Hey guys, I'm not really a math/science type so this is tough for me.

But I need to graph a set of price data znd the best fit line, and the -1 and -2 standard deviations. That should be 68% and 95% correct?

I've been using excel.

I can graph the data really easy as a scatterplot and add a linear fit. But then I how do I graph the standard deviations though?

Please someone help!
 
right-click on your data points (in the graph)
format data series
over there you can specify x and/or y error bars for a particular percentage, abs value, or +/- x (ex: 1 or 2) standard deviations.

This is what I used for Excel 2003, I'd imagine it'd be similar in other versions as well.

Hope this helps.
 
A google search (gnuplot windows download) turns up a long list of windows versions:

http://archives.math.utk.edu/software/multi-platform/gnuplot/msdos/ (one such link, note this is an older version of the software).

Latest version, compiled for Windows available here:

<a target=_blank class=ftalternatingbarlinklarge href="ftp://ftp.gnuplot.info/pub/gnuplot/gp400win32.zip">ftp://ftp.gnuplot.info/pub/gnuplot/gp400win32.zip</a>

The website also has instructions for compiling for windows.

Mac OSX compilations are also readily available.
 
Well if you wnat something similar to the gnuplot graph...could you potentially calculate and plot (as seperate data series) say +/- x deviations---you could these data series together through a line, and remove the point markers as well.

I'm not sure if this will work though, as I've never tried it.
 
Originally posted by: cation555
Well if you wnat something similar to the gnuplot graph...could you potentially calculate and plot (as seperate data series) say +/- x deviations---you could these data series together through a line, and remove the point markers as well.

I'm not sure if this will work though, as I've never tried it.
Click to expand...


Well, honestly this is really going to sound stupid but I have no idea how to actually calculate the standard deviations. I took stats in HS about 9 years ago, and I'm a law student now so stats is not my forte exactly. Believe me I've googled how to do all this a ton of times, AT is my last place for to figure out how to do all this. I tried to figure out how to calculate the numbers and then graph them as a line but its not working apparently either.

How do I caclulate a standard deviation?

 
To calculate standard deviation in Excel, just type '=stdev(range of cells)'. To calculate the mean of this data, type '=average(range of cells)'. Then, to make those lines, you simply take the equation for the best fit (y=m*x+b) and add/subtract 1 or 2 standard deviations to b. Drag this formula down and add it as a new series on the figure - it will be a straight line.
 
Thanks Cyclowizard, I'm trying to remember all my HS algebra in doing this. I remember that M is the slope of the graph at least.

Damn tough for me though.
 
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