log standard deviation

bgo · September 29th, 2004, 1:20 pm

If i have a list of numbers in excel that are all above zero should i use a lognormal distribution if i am trying to get the correct standard deviation of the group? and what function in excel allows me to get this lognormal standard deviation?Thanks

luebke · September 29th, 2004, 3:26 pm

STDEV is the Excel command for the standard deviation.Standard deviation is ALWAYS the same number and just sticks to data, not to a distribution. If you want to have STDEV(x_i) or STDEV(log(x_i)) - now, that is your decision. Do not get confused about the parameters of a distribution and the sample moments of some data.If you want to find a distribution which fits your data, try some, and use KS test to get goodness-of-fit results.

bgo · September 29th, 2004, 3:38 pm

Thanks Luebke!I am not quite sure what KS stands for? is it an excel function?also, after i find the standard deviation of the naturally logged data would i use the excel function =EXP() to find the actual standard deviation number un-logged?Thanks