[MUSIC] Whenever developers sit down to write mobile apps, they make a ton of educated guesses about what their users really want from that app. Some of those decisions will be right on, and some won't. Some will be pretty good for an initial period, but then lose their effectiveness over time. So it can be very important for developers to know just how effective their decisions really are. Now one way to get that information might be to solicit reviews or comments from users. And that's good, but that data can be slow to arrive, and might reflect only your most vocal users. Another way to get that information might be to assemble focus groups so you can directly ask your users about your app. That's also great, but also tends to be a slow process, and can also be pretty expensive, so it's often limited to just a small sample of users. A third option, one that we'll hear about today, is to build your app so it can tell you itself how it's being used. To discuss this, our friends at Amazon have created a short video talking about analytics, how to build data collection into your app, and talking about A/B testing, an approach that allows you to provide different experiences to different users and then directly measure the affect of those differences. And when done right, A/B testing allows you to experiment with, and then dynamically optimize your app for whatever criteria you think most important. So please go to this link and let our friends at Amazon show you how to let data guide your way.