Mean: sum ÷ count

↳4,6,8,10 → mean = 28/4 = 7

Median: middle value when sorted

↳1,3,5,7,9 → median = 5

Mode: most frequent

↳2,4,4,6,8,4 → mode = 4

Range: max − min

↳12,5,18,9,7 → 18 − 5 = 13

Variance: average of (x − mean)²

↳data {2,4,4,4,5,5,7,9} → variance = 4

Std Dev: √variance

↳√4 = 2