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Puzzle for Today

Puzzle No. 80 - Friday Oct 20

We have all heard the saying: “Red sky at night, shepherd’s delight…red sky in the morning, shepherd’s warning”.

Let’s say that our shepherd makes his weather predictions based on the morning sky, predicting a storm when the sky is red and no storm when there are clear skies.

Assume that there is a storm, on average, every second day and a red sky in the morning can be expected every fourth day and always means a storm. How often will the shepherd be correct?

Today’s #PuzzleForToday has been set by Dr Jennifer Rogers, vice president for external affairs for The Royal Statistical Society. Jennifer is Director of Statistical Consultancy at the University of Oxford.

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