attribution errors we talked briefly about attribution errors earlier this is if you are actually using downstream behavior from changeand that gets into gray area you need to understand how you're actually counting those conversions as function of distance from the thing that you changed and agree with your business stakeholders upfront as to how you're going to measure those effects you also need to be aware of if you're running multiple experiments at oncewill they conflict with one anotheris there page flow where someone might actually encounter two different experiments within the same sessionif sothat' going to be problem and you have to apply your judgment as to whether these changes actually could interfere with each other in some meaningful way and affect the customersbehavior in some meaningful way againyou need to take these results with grain of salt there are lot of things that can skew results and you need to be aware of them just be aware of them and make sure your business owners are also aware of the limitations of / tests and all will be okay alsoif you're not in position where you can actually devote very long amount of time to an experimentyou need to take those results with grain of salt and ideally retest them later on during different time period summary in this we talked about what / tests are and what are the challenges surrounding them we went into some examples of how you actually measure the effects of variance using the -statistic and -value metricsand we got into coding and measuring -tests using python we then went on to discuss the short-term nature of an / test and its limitationssuch as novelty effects or seasonal effects that also wraps up our time in this book congratulations for making it this farthat' serious achievement and you should be proud of yourself we've covered lot of material here and hope that you at least understand the concepts and have little bit of hands-on experience with most of the techniques that are used in data science today it' very broad fieldso we've touched on little bit of everything there soyou knowcongratulations again