how to attribute conversions another thing to watch out for is attributing conversions to change downstream if the action you're trying to drive doesn' happen immediately upon the user experiencing the thing that you're testingthings get little bit dodgy let' say change the color of button on page athe user then goes to page and does something elseand ultimately buys something from page wellwho gets credit for that purchaseis it page aor page bor something in-betweendo discount the credit for that conversion depending on how many clicks that person took to get to the conversion actiondo just discard any conversion action that doesn' happen immediately after seeing that changethese are complicated things and it' very easy to produce misleading results by fudging how you account for these different distances between the conversion and the change that you're measuring variance is your enemy another thing that you need to really internalize is that variance is your enemy when you're running an / test very common mistake people make who don' know what they're doing with data science is that they will put up test on web pageblue button versus orange buttonwhatever it isrun it for weekand take the mean amount spent from each of those groups they then say "oh lookthe people with the blue button on average spent dollar more than the people with the orange buttonblue is awesomei love bluei' going to put blue all over the website now!butin factall they might have been seeing was just random variation in purchases they didn' have big enough sample because people don' tend to purchase lot you get lot of views but you probably don' have lot of purchases on your website in comparisonand it' probably lot of variance in those purchase amounts because different products cost different amounts soyou could very easily end up making the wrong decision that ends up costing your company money in the long runinstead of earning your company money if you don' understand the effect of variance on these results we'll talk about some principal ways of measuring and accounting for that later in the