 Chapter four in our book is variability or looking at how much scores differ from one another and Like we had with central tendency. There are several different ways of measuring that so in terms of what we're gonna talk about We're gonna talk about variability in general But things like the range the intercortail range the variance and the standard deviation in particular and the reason We study those is because those are used for things like Determining whether you have outliers in your distribution. They're also used for calculating things like Standard deviations and standard errors and doing inferential statistics So they lead into a lot of other procedures that we're gonna do So that's a good reason but in terms of what you can use these for in the real world It's just nice to know what kinds of things vary a lot and what kinds of things don't So for instance, some things are really consistent If you're going to be in the military, you know what division you're in You know what your rank is your years of service You can predict how much money you're gonna make really well Same thing if you're teaching in the public K through 12 system the pay is very consistent on the other hand If you're an entrepreneur or business owner, it can be anywhere from zero dollars up to millions of dollars It's highly variable and the problem with Variabilities well it sometimes of interest in and of itself is it can also be noise It's hard to settle in on what the true meaning or most representative things going on are in your data So if you're trying to figure out how much a house costs in the neighborhood But the houses are going from ten thousand dollars to ten million dollars. It's it's hard to plan around that. I Know people who work as consultants and sometimes they have zero clients for a month And then they have ten clients in another month and it's all over the place that kind of variability It's important to identify how much is there and how can you plan around it? It's one of the reasons for instance, if you ever were to buy stocks, they tell you buy a mutual fund Which combines lots of different swans because that tends to be more stable and more predictable over time So when you're trying to make decisions It's easy to make decisions with things that are stable and predictable But it's hard to make decisions when things fluctuate all over the place And so you want to know how variable your data are and that's the purpose the point of These different measures of variability and how you can use them both in research and in your own decision making