Variance - Algebra 2

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Question

What is the variance of the following set of numbers?

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Answer

Remember that the variance of a set of numbers is equal to its standard deviation squared. So if the formula for standard deviation is known to be:

Then the variance is simply , given by the following equation:

Where is the variance, N is the number of values in the set, is the number currently being evaluated in the summation, and is the mean of the set. So all we must do to find the variance is determine our mean, and then sum the values given by subtracting the mean from each number in the set and squaring it, dividing the final sum by N to give us our variance. We start by determining the mean of the set:

We then find each value that will be added together by subtracting our mean from each of the numbers in our set and then squaring the result:

Looking at our formula for variance, all we must do now is add these values together and divide by N:

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