Elimination of the disturbing influencing variables
The A/B test or multivariate test is designed to eliminate different influences on different test groups. The test groups are shown different variations of the website at the same time so that all external factors are equal.
As an example, we will look at the online ticket sales of a large cinema. The design of the cinema website is very colorful and full of different graphic elements in the original (A) and very simple and tidy in the test variant (B). Now, it may happen that on weekdays, children and teenagers are more likely to buy movie tickets, which are more attracted by the colorful design. Thus, on weekdays, the original site would perform better than the test variant. If, on weekends, many more adults buy cinema tickets who are attracted by the simple design, this would change and the test version would perform better. If, in addition, more tickets were sold in absolute numbers at the weekend than during the rest of the week, the decision must be made in favour of the test version.
However, if the A/B test had only been carried out on five weekdays, the cinema operators would have opted for the colourful original page without noticing that the weekend sales figures would have reversed the ratio.