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Conditional Probability

Conditional Probability

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Question 270

An ecological study analyzed 400 quadrats (sampling areas) in a nature reserve to record the presence of three rare plant species:

  • Alpine Saxifrage (AAA)
  • Bluebell (BBB)
  • Common Spotted Orchid (CCC)

The findings are summarized in the following table:

Species PresenceAAABBBCCCAAA and BBBAAA and CCCBBB and CCCAll three
Number of quadrats22015013080706040
a.

Represent this information by fully completing a Venn diagram. The region for Alpine Saxifrage only (AAA but not BBB or CCC) has been pre-filled with the number 110.

Three-set Venn diagram for plant species A, B and C, with 110 pre-filled in the A-only region.

[4]
b.

A quadrat is selected at random from the study. Calculate the probability that the quadrat:

(i) contains Alpine Saxifrage only.

(ii) contains at least two of the three rare plant species.

(iii) contains Alpine Saxifrage or Bluebell or both, given that it does not contain the Common Spotted Orchid.

[6]
c.

Determine whether the presence of Bluebells and the presence of Common Spotted Orchids are independent events. Fully justify your answer.

[3]
Markscheme

Conditional Probability Questions

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

368 exam-style questions on Edexcel A Level Maths Conditional Probability, covering 2.1 Set Notation, 2.2 Conditional Probability, 2.3 Conditional Probabilities in Venn Diagrams, 2.4 Probability Formulae, and 2.5 Tree Diagrams. Each one has a worked solution and a mark scheme showing where the marks go.

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