Experimentation is the theme of the SDForum Business Intelligence SIG so far this year. The March meeting featured Deepak Nadig, a Principal Architect at eBay, talking about "Building Better Products Through Experimentation". Experimentation is an important technique for Business Intelligence, although its first uses were with medicine. In 1747, James Lind, a British naval surgeon performed a controlled experiment to find a cure for scurvy. In his book "Supercrunchers", Ian Ayres describes how the Food and Drug Administration has used experimentation since the 1940s to determine whether a medical treatment is efficacious.
While eBay has always used experimentation test and fine tune its web pages, in recent years the process has been formalized. While anyone can propose an experiment, product managers are the group of people who are most likely to do so. Deepak took us through the eBay process and discussed issues with using experimentation. Because they have the infrastructure, simple experiments can be set up within a matter of days. eBay usually runs an experiment for at least a week so that it is exposed to a full cycle of user behavior. Simple experiments to test a small feature typically run for a week or so, larger experiments may run for a month or two and some critical tests run continuously.
For example, eBay is interested in whether it is a good idea to place advertising on their pages. On the one hand it brings in extra revenue in the short term, on the other hand, it might cannibalize revenue in the long term. Experimentation has shown that advertising is a good thing in some situations, however its use is being monitored by some long term experiments to ensure that it remains beneficial.
Deepak took us through some of the issues that with experimentation. One issue is concurrency, how many experiments can be carried out at the same time. As eBay has a high traffic web site, they can get good results with experiments on a small proportion of the users, at most a few percent. As each experiment uses a small percentage of the users, several experiments can be run in parallel. Another issue is establishing a signal to noise ratio for experiments to ensure that experiments are working and giving valid results. eBay has done some AB experiments where A and B are exactly the same to establish whether their experimental technique has any biases.