# Statistics... Regression help!!!?

Statistics. Regression equation??!!?

Biochemical oxygen demand (BOD) measures organic pollutants in water by measuring the amount of oxygen consumed by microorganisms that break down these compounds. BOD is hard to measure accurately. Total Organic Carbon (TOC) is easy to measure, so it is common to measure TOC and use regression to predict BOD

REGRESSION EQUATION:

BOD= -55.43+1.507 TOC

What is the predicted BOD when TOC=0? Values of BOD less than 0 are impossible (when TOC= 0 value of BOD is -55.43) Why does the prediction give an impossible value?

### 1 Answer

- BeeFreeLv 78 years agoFavorite Answer
JJ -

It's simply an extrapolation of the "straight" linear regression line and means nothing if it is outside the data provided that made up the regression.

It is important to remember that you should never "extrapolate" beyond the actual data. I don't know anything about TOC values, but as an example, if the actual data of TOC was in the range 50 to 100, then don't input values for TOC in the regression equation that are less than 50 or more than 100.

Hope that helps

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