charts & graphs

[Guest]

does anyone know how to create a normal curve graph in the chart wizard? i
know the mean and the standard deviation

 

[Guest]

Hi,

Well, you have to calculate probabilities for a series of x values using the
Gaussian probability distribution function.

P = 1/(stdev*sqrt(2 pi))*exp(-0.5*((x-mean)/stdev)^2)


For example, if mean is 1.2 and standard deviation is 0.3:

Create in column A, x-values that are about 4 standard deviations plus/minus
from the mean (in this example, 0 to 2.4) in small increments;
So A2, A3, .... A26 could be 0, 0.1, 0.2, ............ 2.4.
For convenience place the mean and standard deviation is two cells, say D2
and E2 respectively.
Now you can calculate the probability for each x value as follows:
In B2 enter the following formula:
=1/($E$2*SQRT(2*PI()))*EXP(-0.5*((A2-$D$2)/$E$2)^2)
and fill-in the formula down to B26.

Now make an XY-Scatter plot of B2:B26 versus A2:A26.

Regards,
B. R. Ramachandran

 

[Herbert Seidenberg]

Excel already gives you the formula NORMDIST in Data Analysis.
To match the amplitude of the normal curve to your histogram
multiply by sample size and by increment.
A macro on a CD that comes with
Data Analysis with MS Excel
by Berk and Carey
does everything for you automatically.

 

[Guest]

Thanks!

 

[Guest]

Thank you!

Hi,

Well, you have to calculate probabilities for a series of x values using the
Gaussian probability distribution function.

P = 1/(stdev*sqrt(2 pi))*exp(-0.5*((x-mean)/stdev)^2)


For example, if mean is 1.2 and standard deviation is 0.3:

Create in column A, x-values that are about 4 standard deviations plus/minus
from the mean (in this example, 0 to 2.4) in small increments;
So A2, A3, .... A26 could be 0, 0.1, 0.2, ............ 2.4.
For convenience place the mean and standard deviation is two cells, say D2
and E2 respectively.
Now you can calculate the probability for each x value as follows:
In B2 enter the following formula:
=1/($E$2*SQRT(2*PI()))*EXP(-0.5*((A2-$D$2)/$E$2)^2)
and fill-in the formula down to B26.

Now make an XY-Scatter plot of B2:B26 versus A2:A26.

Regards,
B. R. Ramachandran