How Sure Do I Need to Be?
Online marketers often make the mistake of looking only at the descriptive statistics for their test and neglect to even do basic inferential statistics to see if their answers are due simply to random chance. They often do not have the knowledge or discipline to specify the desired confidence in their answer ahead of time, and to patiently collect enough data until that level of confidence is reached.
There are three common issues associated with lack of statistical confidence.
Collecting Insufficient Data
Early in an experiment when you have only collected a relatively small amount of data, the measured conversion rates may fluctuate wildly. If the first visitor for one of the page designs happens to convert, for instance, ...