 There's one final procedure I want to talk about in terms of data sourcing and making new data. It's a form of experimentation. It's simply called AB testing, and it's extremely common in the web world. So for instance, I just barely grabbed a screenshot of Amazon.com's homepage. And you've got these various elements on the homepage. And I just noticed, by the way, when I did this, that this woman is actually a animated gift. So she moves right on. That was kind of weird. Never seen that before. But the thing about this is this entire layout, how things are organized and how they're on there will have been determined by variations on a B testing by Amazon. Here's how it works. For your web page, you pick one element like what's the headline or what are the colors or what's the organization or how do you word something? And you create multiple versions, maybe just to version A and version B, which is why he called AB testing. And then when people visit your web page, you randomly assign those visitors to one version or another, you have software that does that for you automatically. And then you compare the response rates on some response, I'll show you those in a second. And then once you have enough data, you implement the best version, you sort of set that one solid, and then you go on to something else. Now in terms of response rates, there's a lot of different outcomes you can look at. You can look at how long a person's on a page, you can actually do mouse tracking if you want to. You can look at click throughs. You can also look at shopping cart value and or abandonment, a lot of possible outcomes. All of these contribute through AB testing to the general concept of website optimization, to make your website as effective as it can possibly be. Now the idea also is that this is something you're going to do a lot. You can perform AB tests continually. In fact, I've seen one person say that what AB testing really stands for is always be testing, kind of cute, but it does give you the idea that improvement is a constant process. Now if you want some software to do AB testing, two of the most common choices are optimizly and VWO, which stands for visual web optimizer. Now many others are available, but these are especially common. And when you get the data, you're going to use statistical hypothesis testing to compare the differences or really the software does it for you automatically, but you may want to adjust the parameters because most software packages cut off testing a little too soon and the information is not quite as reliable as it should be. But in some, here's what we can say about AB testing is a version of website experimentation done online, which makes it really easy to get a lot of data very quickly. It allows you to optimize the design of your website for whatever outcome is important to you. And it can be done as a series of continual assessments, testing and development to make sure that you're accomplishing what you want to as effectively as possible for as many people as possible.