Question Statement:
In a border irrigation test, water depths infiltrated along 4 check points are 10 cm, 8 cm, 12 cm, and 10 cm. The mean infiltrated depth is $d = 10\text{ cm}$. Numerical deviations from the mean are $|10-10|=0$, $|8-10|=2$, $|12-10|=2$, and $|10-10|=0$, giving average numerical deviation $y = \frac{0+2+2+0}{4} = 1.0\text{ cm}$. Water distribution efficiency in % is: