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2.3 Probability

2.3 Probability

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Question 141

A conference organizer surveyed 40 attendees regarding their participation in the Keynote speech and the Technical Workshop. He found that, of the 40 attendees:

  • 25 attended the Keynote speech
  • 16 attended the Technical Workshop
  • 10 attended both the Keynote and the Workshop
a.

An attendee is chosen at random from the 40 surveyed. Determine whether the event 'the attendee attended the Keynote speech' and the event 'the attendee attended the Technical Workshop' are independent.

[2]
b.

For a regional library network, it is known that:

  • the probability that a registered user borrows an e-book is P(E)=25P(E) = \frac{2}{5}P(E)=52​
  • the probability that a registered user borrows an audiobook is P(A)=37P(A) = \frac{3}{7}P(A)=73​
  • the probability that a registered user borrows an audiobook given that they borrow an e-book is P(A∣E)=14P(A|E) = \frac{1}{4}P(A∣E)=41​

Calculate the probability that a registered user borrows an e-book or an audiobook or both.

[3]
Markscheme

2.3 Probability Questions

  1. A Level
  2. /Maths
  3. /2.3 Probability

200 exam-style questions on OCR A Level Maths 2.3 Probability, covering 2.3.1 Mutually exclusive and independent events, 2.3.2 Diagrams to assist probability calculations, 2.3.3 Conditional probability (A-level only), 2.3.4 Conditional probability from first principles (A-level only), and 2.3.5 Modelling with probability. Each one has a worked solution and a mark scheme showing where the marks go.

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