Lognormal formulas

[ldarley]

Hi all,

I'm a bit confused about what value I'm supposed to use in the lognormal.dist and other lognormal formulas for the mean and standard deviation parameters.

For example if my x range is in B:B and the log of x is in range C:C is the mean:

1: Average(B:B)
2. Average(ln(B:B))
3. Average (C:C)

Same options for standard deviation. Any help greatly appreciated!

Laurence

 

[ldarley]

Sorry 2. was supposed to be ln(average b:b))

 

[joeu2004]

Use ranges like B1:B10000 instead of B:B. Adjust 1 and 10000 as needed. But the point is: it is unlikely that you have 1+ million data points.


As the lognormal.dist help page explains, the mean parameter is the "mean of ln(x)"; and the std dev parameter is the "standard deviation of ln(x)".

So array-enter (press ctrl+shift+Enter instead of just Enter) the following formulas:

=AVERAGE(LN(B1:B10000))

=STDEVP(LN(B1:B10000))

Use STDEV instead of STDEVP if B1:B10000 is a sampling, and you want to estimate the (larger) population std dev.


[EDIT] I just noticed that you have ln(x) in C:C. So you could normally-enter (press Enter usual) the following formulas:

=AVERAGE(C1:C10000)

=STDEVP(C1:C10000)

 

[ldarley]

Awesome joeu2004 thanks for your help, particularly the array formula!