Taking the logorithm of data items can sometimes be a useful form of data transformation in several circumstances. A logorithmic transform turns exponential growth onto linear grpwth, so can be useful for long term financial data where value of money gradually reduces in value due to inflation. It can also be used where the variability grows with the size of data items, which is freqently the case for certain kinds of time measurements. If you are measuring time delays often larger values also have larger variability. If the logarithm of data follows the Normal distribution, the data is known as log-normal.
Used on pages 203, 330
Also known as logarithmic transformation