Edexcel S3 2023 June — Question 5

Exam BoardEdexcel
ModuleS3 (Statistics 3)
Year2023
SessionJune
TopicLinear combinations of normal random variables
TypeKnown variance confidence interval

  1. The continuous random variable \(X\) is normally distributed with
$$X \sim \mathrm {~N} \left( \mu , 5 ^ { 2 } \right)$$ A random sample of 10 observations of \(X\) is taken and \(\bar { X }\) denotes the sample mean.
  1. Show that a \(90 \%\) confidence interval for \(\mu\), in terms of \(\bar { x }\), is given by $$( \bar { x } - 2.60 , \bar { x } + 2.60 )$$ The continuous random variable \(Y\) is normally distributed with $$Y \sim \mathrm {~N} \left( \mu , 3 ^ { 2 } \right)$$ A random sample of 20 observations of \(Y\) are taken and \(\bar { Y }\) denotes the sample mean.
  2. Find a 95\% confidence interval for \(\mu\), in terms of \(\bar { y }\)
  3. Given that \(X\) and \(Y\) are independent,
    1. find the distribution of \(\bar { X } - \bar { Y }\)
    2. calculate the probability that the two confidence intervals from part (a) and part (b) do not overlap.