Mean of 5 observations is 7 . If four of these observations are 6 , 7 , 8 , 10 and one is missing then the variance of all the five observations is :

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Let 5 th observation be x . Given mean = 7 ​ ∴ 7 = 5 6 + 7 + 8 + 10 + x ​ ⇒ x = 4 ​ Now, Variance = 5 ( 6 − 7 ) 2 + ( 7 − 7 ) 2 + ( 8 − 7 ) 2 + ( 10 − 7 ) 2 + ( 4 − 7 ) 2 ​ ​ = 5 1 2 + 0 2 + 1 2 + 3 2 + 3 2 ​ ​ = 5 20 ​ ​ = 4 ​ = 2 ​

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