Ch32 26
- 1. Exercice 26 N = 10 n=5 p = 0, 3 = R N donc R = 0, 3 × 10 = 3 3 7 C3 · C2 1 (a) P(X = 3) = 10 = C5 12 (b) P(X ≤ 2) P(X ≤ 2) = P(X = 0) + P(X = 1) + P(X = 2) 3 7 C0 · C5 C3 · C7 C3 · C7 = 10 + 1 10 4 + 2 10 3 C5 C5 C5 1 5 5 11 = + + = 12 12 12 12 (c) E(X ) = n · p = 5 × 0, 3 = 1, 5 (d) V (X ) = N−n N−1 · n · p · (1 − p) = 5 9 × 5 × 0, 3 × 0, 7 = 7 12