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Probability density and cumulative distribution functionsEdexcel International A Level Further Maths: Mind map

Continuous variable
The pdf f(x)
The cdf F(x)

pdf and cdf

continuous random variables

f(x)F(x)area = probability
The link
Piecewise
Exam tips

Exam questions on Probability density and cumulative distribution functions

  1. The continuous random variable XX has probability density function f(x)=kx2f(x)=kx^2 for 0≤x≤30\le x\le3, and f(x)=0f(x)=0 otherwise, where kk is a constant.
    Find the cumulative distribution function F(x)F(x) for 0≤x≤30\le x\le3.2 marks
  2. The continuous random variable YY has cumulative distribution function F(y)=0F(y)=0 for y<1y<1, F(y)=y2−18F(y)=\frac{y^2-1}{8} for 1≤y≤31\le y\le3, and F(y)=1F(y)=1 for y>3y>3.
    Find P(1.5<Y≤2.5)P(1.5<Y\le2.5).2 marks
  3. The continuous random variable XX has probability density function f(x)=kxf(x)=kx for 0≤x≤20\le x\le2, f(x)=k(6−2x)f(x)=k(6-2x) for 2<x≤32<x\le3, and f(x)=0f(x)=0 otherwise, where kk is a constant.
    Show that k=13k=\frac13.3 marks
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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).