AQA S3 2015 June — Question 2

Exam BoardAQA
ModuleS3 (Statistics 3)
Year2015
SessionJune
TopicLinear combinations of normal random variables
TypeConfidence interval for single proportion

2 Emilia runs an online perfume business from home. She believes that she receives more orders on Mondays than on Fridays. She checked this during a period of 26 weeks and found that she received a total of 507 orders on the Mondays and a total of 416 orders on the Fridays. The daily numbers of orders that Emilia receives may be modelled by independent Poisson distributions with means \(\lambda _ { \mathrm { M } }\) for Mondays and \(\lambda _ { \mathrm { F } }\) for Fridays.
  1. Construct an approximate \(99 \%\) confidence interval for \(\lambda _ { \mathrm { M } } - \lambda _ { \mathrm { F } }\).
  2. Hence comment on Emilia's belief.