Question

Suppose X ~ B(n, p) and P(X = 3) = P(X = 5). If p > 1/2, then

• A. n £ 7
• B. n > 8
• C. n  9
• D. None of these

Answer 1

Answer: (A)

n £ 7

Answer 2

ⁿC₃p³(1 – p)^{n – 3}

= ⁿC₅p⁵(1–p)^n–5

Ž $\frac { ( \mathrm { n } - 3 ) ( \mathrm { n } - 4 ) } { 2 \theta } = \frac { ( 1 - \mathrm { p } ) ^ { 2 } } { \mathrm { p } ^ { 2 } } < 1$Ž n £ 7