CAIE S2 2020 June — Question 3

Exam BoardCAIE
ModuleS2 (Statistics 2)
Year2020
SessionJune
TopicApproximating the Binomial to the Poisson distribution
TypeState Poisson approximation with justification

3 In the data-entry department of a certain firm, it is known that \(0.12 \%\) of data items are entered incorrectly, and that these errors occur randomly and independently.
  1. A random sample of 3600 data items is chosen. The number of these data items that are incorrectly entered is denoted by \(X\).
    1. State the distribution of \(X\), including the values of any parameters.
    2. State an appropriate approximating distribution for \(X\), including the values of any parameters. Justify your choice of approximating distribution.
    3. Use your approximating distribution to find \(\mathrm { P } ( X > 2 )\).
  2. Another large random sample of \(n\) data items is chosen. The probability that the sample contains no data items that are entered incorrectly is more than 0.1 . Use an approximating distribution to find the largest possible value of \(n\).