A multivariate test is a logical continuation of an A\B test topic. Instead of comparing only two variants (A\B test) you can compare more than two - multivariate test (MVT).
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Let's imagine you have a headline and a button in two versions. You want to find out which combination of a headline and a button will lead to a higher conversion. With MVT you can compare each version of a button and each version of a headline. This means you will have four variants to test.
Multivariate tests normally allow you to test more variants at the same time. That will allow you to get results quicker.
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Multivariate testing vs A\B (split) testing ?
The main difference of multivariate tests is that you can simultaneously test several elements of a page instead of testing one thing at the time (A\B test).Let's imagine you have a headline and a button in two versions. You want to find out which combination of a headline and a button will lead to a higher conversion. With MVT you can compare each version of a button and each version of a headline. This means you will have four variants to test.
What's the difference between multivariate test and pairs of A\B tests ?
Thing is, you need to run A\B test in isolation. To get clear, representable results you need to run one A\B test at a time on a single page. Which brings in certain limitations.Multivariate tests normally allow you to test more variants at the same time. That will allow you to get results quicker.
Disadvantages ?
The more options you'll test the more fragmented your traffic distribution is going to be. In a case of an A\B test your traffic split is 50\50. While if you want to test four options in a multivariate test your traffic split will be 25\25\25\25. To get reliable results - traffic groups should contain enough participants (sample size). In a case of an MVT, this requirement could be fulfilled only by a large amount of traffic.When do A\B test and when do MVT ?
For major changes and drastically different options - make an A\B test.
For marginal improvements and conversion optimization - make an MVT.
Have a lot of traffic and a lot of ideas ? - make an MVT.
Have one metric to improve and best guess how ? - make an A\B test.
Start with an A\B test, because it's simple. Continue with MVT to reach top conversion.
An hour long webinar on A\B and MVT: