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A weather forecast says - the probability that it will rain on Monday is 0.55 - and - the probability that it will rain on Tuesday is 0.25 - OCR - GCSE Maths - Question 8 - 2020 - Paper 1
Question 8
A weather forecast says - the probability that it will rain on Monday is 0.55 - and - the probability that it will rain on Tuesday is 0.25. Ella draws a tree diagr... show full transcript
Worked Solution & Example Answer:A weather forecast says - the probability that it will rain on Monday is 0.55 - and - the probability that it will rain on Tuesday is 0.25 - OCR - GCSE Maths - Question 8 - 2020 - Paper 1
Step 1
Write down three errors that Ella has made with her tree diagram.
Answer
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The probability of rain on Tuesday should be 0.25 and the probability of not raining should thus be 0.75, not 0.75 rain and 0.25 not rain as shown.
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The complementary probabilities for each day must sum to 1. For Monday, the probability of not raining should be 1 - 0.55 = 0.45, not 0.35 as displayed.
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Ella did not include the total probabilities for both days correctly in the tree diagram, which may lead to confusion when calculating joint probabilities.