Graphing a data set with standard deviations?

[astroview]

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!

 

[cation555]

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.

 

[astroview]

Well the problem with that is I have a lot of data, so the graph essentially becomes one big blob when I do that.

Ideally I'd like to get the graph to look sorta like this:
http://invest.kleinnet.com/bmw1/stats30/

The guy did that in gnuplot, but that's only available in linux apparently which I do not run.

 

[cation555]

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.

 

[astroview]

Any idea how to do it easily in excel though?

 

[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.

 

[astroview]

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.

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?

 

[CycloWizard]

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.

 

[astroview]

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.