WEBVTT 00:00:00.200 --> 00:00:03.450 Normal distributions generally look like this. Although their 00:00:03.450 --> 00:00:05.130 width and center can change based on the 00:00:05.130 --> 00:00:09.080 distribution's parameters. There are two parameters associated with 00:00:09.080 --> 00:00:12.790 a normal distribution. The mean, mu. And the standard 00:00:12.790 --> 00:00:16.030 deviation, sigma. These two parameters plug in to 00:00:16.030 --> 00:00:18.870 the following probability density function, which describes a 00:00:18.870 --> 00:00:21.940 Gaussian distribution. The expected value of a variable 00:00:21.940 --> 00:00:25.030 described by a Gaussian distribution is the mean, mu. 00:00:25.030 --> 00:00:27.370 and the variance is the standard deviation, sigma 00:00:27.370 --> 00:00:30.310 squared. Normal distributions are also symmetric about their 00:00:30.310 --> 00:00:32.920 mean. If you've taken an introduction to stats 00:00:32.920 --> 00:00:35.300 course, the normal distribution should be a familiar tool.