The notion of an effective value is used in almost all scientific disciplines. It refers to a weighted average of some value, weighted by frequency. That is, you multiply the value for each case by the frequency (percentage/100) for that case, and add up all such products. This can be written as a formula as follows.
Effective Value = Value1×Frequency1 + Value2×Frequency2 + ... + Valuen×Frequencyn
The computation of an effective average can be conveniently put into a tabular form as shown below.
| Value | Frequency | Product |
|---|---|---|
| Value1 | Frequency1 | Value1×Frequency1 |
| Value2 | Frequency2 | Value2×Frequency2 |
| . | . | . |
| . | . | . |
| . | . | . |
| Valuen | Frequencyn | Valuen×Frequencyn |
| Effective Value = | sum of above entries | |