课程: Probability Foundations for Data Science

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Variance and standard deviation

Variance and standard deviation

课程: Probability Foundations for Data Science

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Variance and standard deviation

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- [Instructor] Let's take some time to learn about variance and standard deviation. Variance is how you measure the spread of random variables and probability. It is what is called a measure of dispersion. This is often paired with the expected value to better describe your random variable. This way you know how your random variable averages, along with how spread out the values can be for it. It is often used when designing experiments to help determine sample size and analyze the variability within and between experimental groups. Let's look at a formal definition for variance. For random variable X, you can determine its variance by finding the expected value of variable X, subtracted by the expectation of X squared. As you see, expectation is still heavily involved when calculating variance. In this course, it will be denoted as V-A-R X, but note that it is sometimes denoted as sigma squared. Standard deviation is another measure of dispersion that helps measure how spread out…

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