Skip to content
MathsGenie logo
Quick links
Open app

Course home

  1. A Level
  2. Maths OCR (MEI)
  3. Question bank

2.3.10 Conditional probabilities (A-level only)

MediumHard
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899
Question 91

The continuous random variable T T\,T represents the operational lifespan, in days, of a bioluminescent underwater sensor. The probability density function of T T\,T is modeled by:

f(t)={c(25−t2)0≤t≤50otherwise f(t) = \begin{cases} c(25 - t^2) & 0 \le t \le 5 \\ 0 & \text{otherwise} \end{cases} f(t)={c(25−t2)0​0≤t≤5otherwise​

where c c\,c is a constant.

a.

Show that c=3250\displaystyle c = \frac{3}{250}c=2503​.

[2]
b.

Determine the cumulative distribution function F(t)F(t)F(t) for the interval 0≤t≤50 \le t \le 50≤t≤5.

[2]
c.

Calculate the probability that a randomly selected sensor remains operational for more than 3 days.

[2]
d.

Given that a sensor has already functioned for 3 days, determine the probability that it will last for at least 4 days in total.

[3]
e.

Five such sensors are deployed independently. Find the probability that exactly 2 of them remain operational for more than 3 days.

[3]

2.3.10 Conditional probabilities (A-level only) Questions

  1. A Level
  2. /Maths
  3. /2.3.10 Conditional probabilities (A-level only)