Context for question 3
In the work done by a typesetting department, incorrect characters appear randomly and independently at a constant average rate of 5 incorrect characters per 100 pages.
May/June 2026 Paper 61
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Context for 3(a)
A book that is typeset in the department contains 500 pages. The number of incorrect characters in the book is denoted by .
3(a)(i)Poisson DistributionEasy1 mark
State the distribution of , including the values of any parameters.
3(a)(ii)Normal Distribution Normal ApproximationsHard2 marks
State an appropriate approximating distribution for , including the values of any parameters.
Justify your choice of approximating distribution.
Approximating distribution
Justification
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3(a)(iii)Normal Distribution Normal ApproximationsMedium3 marks
Use your approximating distribution to find .
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Probability
3(b)Normal Distribution Normal ApproximationsHard5 marks
Another book that is typeset in the department contains pages. The probability that the book contains fewer than 18 incorrect characters is less than .
Use an approximating distribution to find the largest possible value of .
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