The mean of the given data is (18 + 20 + 18 + 2 + 7)/5 = 13

To calculate the variance we need to find the difference between each term of the data, find the square of the value and then determine the average of the squares.

18 - 13 = 5 , 20 - 13 = 7, 18 - 13 = 5, 2 - 13 = -11 and 7 - 13 = -6.

The average of the square is:

(5^2 + 7^2 + 5^2 + 11^2 + 6^2)/5

=> (25 + 49 + 25 + 121 + 36)/5

=> 51.2

**The required variance is 51.2**

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