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The mean of a set of numbers is the sum divided by the number of terms.

Add and .

Add and .

Add and .

Add and .

Add and .

Add and .

Add and .

Factor out of .

Cancel the common factors.

Factor out of .

Cancel the common factor.

Rewrite the expression.

Divide.

Set up the formula for variance. The variance of a set of values is a measure of the spread of its values.

Set up the formula for variance for this set of numbers.

Simplify the numerator.

Subtract from .

Raise to the power of .

Subtract from .

Raise to the power of .

Subtract from .

Raise to the power of .

Subtract from .

Raise to the power of .

Subtract from .

Raise to the power of .

Subtract from .

Raise to the power of .

Subtract from .

Raise to the power of .

Subtract from .

Raise to the power of .

Add and .

Add and .

Add and .

Add and .

Add and .

Add and .

Add and .

Reduce the expression by cancelling the common factors.

Subtract from .

Cancel the common factor of and .

Rewrite as .

Cancel the common factors.

Rewrite as .

Cancel the common factor.

Rewrite the expression.

Approximate the result.

Find the Variance 9 , 10 , 10 , 8 , 7 , 11 , 12 , 9