Hi, I’m Ben Owens. I’m a math educator here for About.com and I’m going to explain Probablilty and how it is important in statistics. Probability is the study of chance. To show how likely or unlikely an event is to occur, we assign it a number and we call that number the probability. This number must be between 0 and 1 (inclusive). If the probability is closer to 0, it means the event is less likely to occur and closer to 1 means it’s more likely to occur. Let’s take a look at an example. I want to know the probability of my peanut butter sandwich falling down with the peanut butter facing down. What’s the chance my floor is going to get smeared with peanut butter? Well, there are only two possible outcomes: the sandwich falls with the right side down, or with the wrong side down.And if we have two possible outcomes, an event has a 50% chance of occuring. That means it has a probability of 0.5. Now let’s take a look at a more complicated example. If you flip a coin twice, you can look for how many times it will land on heads. In this case, There are 4 possible outcomes - Heads Twice, Heads Once on the first flip, Heads First on the 2nd Flip or no heads at all. That’s 3 out of 4 times it could land on heads, so the probability is .75 that we’ll have at least one heads in our flips. In statistics we use probability when making predictions from a sample of the population. This is called Inferential Statistics. Using probability we can show that with a relatively small sample, you can make accurate predictions with a certain level of confidence. We are able to use probability because the sample is chosen at random, which introduces an element of chance into the process. Though people have had an idea of whether events are likely or not for centuries, it wasn’t until the 1600s that probability was more formally studied. The correspondence that is attributed to laying down the groundwork of modern probability was a series of letter between two guys named Pascal and Fermat. In these letters they were discussing a gambling problem that had people stumped! Though useful in games and gambling, probability is vital in many important fields including statistics, economics, engineering, and even quantum physics! For more on math, visit education.about.com. Thanks for watching!