Question Statement:
In an irrigation check basin, four penetration depth measurements are $10\text{ cm}, 12\text{ cm}, 8\text{ cm}, 10\text{ cm}$. The mean depth is $d = 10.0\text{ cm}$. Absolute deviations are $|10-10|=0, |12-10|=2, |8-10|=2, |10-10|=0$. Average deviation is $\bar{y} = (0+2+2+0)/4 = 1.0\text{ cm}$. Water distribution efficiency $\eta_d = 100(1 - \bar{y}/d)$ in percent is: