- #1

paluee

- 1

- 0

I am in the energy industry, and we do linear/multilinear regressions stats.

One of the concepts being introduced to supplement standard way of doing regressions is make use of:

(1) Coefficient of Variation Root Mean Squared Error

(2) Net Mean Bias or Abs (Mean bias)

Unfortunately, I can't find the explicit formula's.

Below is a list one goes thru to ensure a good fit/model,

some of the rules of thumb used in our industry:

*******************************************

1. R2 (Quality of fit): 0.75 or higher, with 1.00 as perfect fit.

2. CVRMSE Eng (Coefficient of Variation Root Mean Squared Error): 25 or lower for consumption meters.

3. CVRMSE Dmd (Coefficient of Variation Root Mean Squared Error): 35 or lower for demand meters.

4. Abs (Mean bias) - Must be equal to or less than 0.005.

5. Abs (T-Stats) - Positive 2.0 or higher for CDD and HDD, and greater than 2.0 or less than

-2.0 for any user variable.

6. HDD and CDD T-Stat > 0. This box must be checked to be ASHRAE and IPMVP

compliant

*******************************************

So in the context of our industry, say one take

a years worth of data, meaning 12 months of data, therefore 12 data points.

One performs a regression on this 12 data points to obtain an equation,

then one tries to interpolate these data points: a01=month1, a02=month2, etc.

Here is some output:

Data||ActualRaw||RegressInterpolatedValues

a01 51520 51345

a02 37120 37738

a03 33280 37512

a04 28800 28757

a05 17920 18641

a06 17280 17953

a07 19200 18965

a08 20800 18727

a09 27200 27243

a10 31040 31719

a11 38720 35605

a12 52480 51028

One of the methods used was to find the sum of each column and get a percent difference, and then get the differences of each month doing

=(actual-Regress)/actual * 100%

This was to get a measure of deviation of the regression to the actualdata.

But I must now use : CVRMSE and Net_Mean_Bias.

Does anybody have the explicit formula's for these 2 statistics.

Hope somebody knows these.

Here is an excerpt from our industry on this:

*************************************

users only heeded the R2 value and T-statistics, keeping them in

the range as detailed above. This was the recognized practice in the energy analysis industry. In the 2002, ASHRAE came

out with Guideline 14, which specified not an R2 value, but instead a CVRMSE and a Mean Bias Error (along with Tstatistics).

The energy analysis industry has been slow to catch on, still relying mostly on the R2 value. This was mostly

due to the fact that the software never had the CVRMSE and Mean Bias Error implemented—making it hard for energy

analysts to tune to these values

*************************************

SO hope some can tell me the formulas, or at least point me

to some source.

Paluee