If the mean and variance of six observations $7,10,11,15 , a , b$ are 10 and $\frac { 20 } { 3 }$, respectively, then the value of $| a - b |$ is equal to: (1) 9 (2) 11 (3) 7 (4) 1
If the mean and variance of six observations $7,10,11,15 , a , b$ are 10 and $\frac { 20 } { 3 }$, respectively, then the value of $| a - b |$ is equal to:\\
(1) 9\\
(2) 11\\
(3) 7\\
(4) 1