Mean, standard deviation, variance — worked example (water class, 3 pixels, 2 bands).

Pixels: (24, 3), (26, 5), (28, 10). Band 1 values: 24, 26, 28. Band 2 values: 3, 5, 10.

\[\bar{Q}_1 = \frac{24 + 26 + 28}{3} = 26 \qquad \bar{Q}_2 = \frac{3 + 5 + 10}{3} = 6\]

Standard deviation formula (k pixels):

\[S_Q \;=\; \sqrt{\frac{\sum_{i=1}^{k} (Q_i - \bar{Q})^2}{k-1}}\]

• Band 1: S_Q₁ = 2
• Band 2: S_Q₂ = 3.6

Variance = std²: Band 1 = 4; Band 2 = 12.96.