Created bell curve in Excel, do not understand the curves i created

#1
Hello everyone,

I was asked to create a bell curve in excel and i didn't know how to do it, so i googled it out and followed the instructions on MS's website.

http://support.microsoft.com/kb/q213930/

Here is the output:

http://img99.imageshack.us/img99/217/bellcurveyz6.jpg

You can't see it all, but Column A is the original data (it's 75 data points) and column D is random numbers generated from this data (it's 2000 data points).

The blue curve seems to be the normal distribution. The other 2 curves, i have no idea what that is. Does anyone know which curve represents the actual data? Thanks!
 

TheEcologist

Global Moderator
#2
Hello everyone,

I was asked to create a bell curve in excel and i didn't know how to do it, so i googled it out and followed the instructions on MS's website.

http://support.microsoft.com/kb/q213930/

Here is the output:

http://img99.imageshack.us/img99/217/bellcurveyz6.jpg

You can't see it all, but Column A is the original data (it's 75 data points) and column D is random numbers generated from this data (it's 2000 data points).

The blue curve seems to be the normal distribution. The other 2 curves, i have no idea what that is. Does anyone know which curve represents the actual data? Thanks!

Lets start with what you are trying to do, what question do you want to answer?
Do you want to see if your original data is normally distributed? or do you only need to plot a bell shaped curve based on your original data? If so see the example I give in the attachment.
 
#3
Lets start with what you are trying to do, what question do you want to answer?
Do you want to see if your original data is normally distributed? or do you only need to plot a bell shaped curve based on your original data? If so see the example I give in the attachment.
I need to plot a normal distribution curve and also a curve to see how much it is skewed from normal distribution... does my graph show this? Someone on another forum answered with this:

Looks like Pink line called Histogram Bin is based on the range G3:G10 as the Y values. X values a sequential 1,2,3 etc. Displayed on the Secondary axis. Point 8 drops to zero as the value "More" is being treated as zero.

Yellow line Histogram Frequency also on the secondary axis is based on H3:H10
Unfortunately, i have no idea what the data i generated using that Microsoft Excel Bell Curve link is... thanks!
 
#4
Actually, i thought about it a little more... the blue line is the normal distribution based on the random data while the purple line is the curve based on the actual data, right?
 

TheEcologist

Global Moderator
#5
I need to plot a normal distribution curve and also a curve to see how much it is skewed from normal distribution... does my graph show this? Someone on another forum answered with this:
"how much it is skewed from normal distribution" and with "it" you mean the distribution of your Original data?

If so I recommend you use a qq-plot. It can tell you how much your data deviates from a normal distribution or how "skewed" it is.

http://en.wikipedia.org/wiki/Q-Q_plot

This is a helpfull file on how to in excel:
http://science.uniserve.edu.au/pubs/callab/vol15/cal15_guan.pdf
 
#6
"how much it is skewed from normal distribution" and with "it" you mean the distribution of your Original data?

If so I recommend you use a qq-plot. It can tell you how much your data deviates from a normal distribution or how "skewed" it is.

http://en.wikipedia.org/wiki/Q-Q_plot

This is a helpfull file on how to in excel:
http://science.uniserve.edu.au/pubs/callab/vol15/cal15_guan.pdf
Thanks for your help, i'll take a look at it... i was asked to create a bell curve though. Maybe this can supplement it.