Skip to content
MathsGenie logo
Quick links
Open app

Course home

  1. A Level
  2. Maths OCR
  3. Question bank

2.4.4 Mean and variance of the binomial (A-level only)

MediumHard
12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455
Question 1

A space agency monitors the deployment of a large constellation of n n\,n small satellites. The number of satellites, SSS, that successfully reach their intended altitude in a single deployment phase is modeled by the discrete random variable S∼B(n,p)S \sim \text{B}(n, p)S∼B(n,p). The mean number of successful deployments is 80.

a.

State the variance of S S\,S in terms of ppp.

[1]
b.

A normal distribution is used as an approximation for SSS. Using this approximation and a continuity correction, it is found that P(S≥92)=0.0301P(S \ge 92) = 0.0301P(S≥92)=0.0301 to 3 significant figures.

Show that 80−80p=6.117\sqrt{80 - 80p} = 6.11780−80p​=6.117 to 4 significant figures.

[3]
c.

Hence find the value of ppp, giving your answer to 2 significant figures.

[2]

2.4.4 Mean and variance of the binomial (A-level only) Questions

  1. A Level
  2. /Maths
  3. /2.4.4 Mean and variance of the binomial (A-level only)