Normal distribution with upper and lower bounds
Jeremy Udkoff
Hello,
I have a number like $5,000, SD50,000 and would like to create a distribution for it. The number shouldn't ever be less than 0. How do I do this?
Thank you so much!
Comments
Use a gamma distribution with alternative parameters ( mean and SD)
Thank you! I tried using a gamma distribution but I get an error because my SD is too large.
It may be that no parametric distribution will fit your cost data very well, Sounds like there are some extreme cost outliers. Another option is to use a table distribution. Create a table with the index being the values to be sampled and the value column being the probability of each value such that the sum down the value column is 1.0. Then create a new sampling distribution of the table type and select the table you just created. Samples will be drawn according to the probabilities in the table.
I think the new Pert distribution introduced in TreeAge Pro 2020 might be very helpful here.
In essence, the Pert distribution functions like a Beta distribution in that it is continuous and bounded. However, the Pert distribution can be bounded by any values, while the Beta distribution is always bounded between 0-1.
Andrew
Pert didn't work unfortunately because I can't specify a mean value (just most likely). However, I think this parameter is so out of normal bounds that it wouldn't fit a parametric distribution anyway.
Thank you!
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