Environmental Project No. 1139 – Comparison of measurering results between solid fuel stoves tested in accordance with EN 13240 and NS 3058

Comparison of measuring results between solid fuel stoves tested in accordance with EN 13240 and NS 3058

3. Terms and Definitions

The result of the examination is available as diagrams, in which the particle emission is shown as a function of CO value and OGC value, respectively. For each graph, a linear regression has been marked with the purpose of illustrating the tendency. An R² value for the linear regression has been stated.

Definition of R², cf. "Complete Business Statistics", Irwin/McGraw-Hill 1999:

The coefficient of determination R² is a descriptive measure of the strength of the regression relationship, a measure of how well the regression line fits the data.

- and furthermore, about the size of R²:

An R² value of 0.9 is very god, a value greater than 0.8 is good, and a value of 0.6 or more may be satisfactory for some applications. When R² value is 0.5 or less, the regression explains only 50% or less of the variation in the data.

If we are interested only in understanding the relationship between the variables, lower values of R² may be acceptable, as long as we understand that the model does not explain much.