Counting Adjacent Heads
A fair coin is flipped 10 times. Let N be the number of positions i (1 ≤ i ≤ 9) such that flips i and i + 1 are both heads. Find Var(N) as a reduced fraction.
Related problems & prerequisites
Worth solving first
- Variance of Two Dice 2.0/10
- Correlation of Sum and Difference 2.0/10
Source: Original problem written for AxiomIQ; variance of a sum of dependent indicators.