[CentralOH] OT: Statistician needed

Eric Floehr eric at intellovations.com
Mon May 16 14:59:44 EDT 2016


Hey all,

I'm in need of some help with statistics, and if anyone has any thoughts on
this, or know someone who could do this, I would appreciate it greatly.

I have a set of errors, normally distributed around 0 error (it's
temperature forecast error). You can assume that the sample of forecasts is
representative of the entire population (for example, taking 50 strategic
locations around the U.S. to represent all U.S. locations).

I then calculate the mean absolute error, and the RMSE. These have some
positive value.

What I would like to calculate on the MAE and RMSE is a confidence interval
that the population error is within given the sample MAE or RMSE and it's
related statistics (sample size, mean error, MAE, RMSE, standard deviation,
etc.).

For example, let's say that one provider's RMSE is 3.18 (A) and another's
is 3.5 (B). I'd like to know with some confidence that there is (or isn't)
a difference between providers (i.e. that provider A confidently has lower
error than B).

Currently, the way I'm doing it is using the normative inverse function in
Excel:

Lower bound: NORMINV(0.005,RMSE,STDDEV_RMSE/SQRT(NUMBER_OF_SAMPLES))

Upper bound: NORMINV(0.995,RMSE,STDDEV_RMSE/SQRT(NUMBER_OF_SAMPLES))

as in section 9.18 of:
http://www.saylor.org/site/wp-content/uploads/2012/10/BUS204-Ling-6.2.pdf

But I'm not at all convinced that I'm doing that right, or that it applies
in this situation.

Thanks so much!
Eric
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