Australia Post claims to deliver 96% of letters on time but only 52 out of 59 letters arrived on time in a study.
In this simulation, the null hypothesis is that the 96% of letters arrive on time:
Click Accumulate and simulate attempts to deliver 59 letters between 100 and 200 times. (Hold down the Simulate button.)
Getting only 52 letters delivered on time would be unlikely if Australia Post's claim was correct so there is strong evidence that fewer than 96% are delivered on time.
Emphasise the general concepts:
The Herald-Sun newspaper published the following article on November 25 1992.
Doubt has been cast over Australia Post's claim of
delivering 96 per cent of standard letters on time.
A survey conducted by the Herald-Sun in Melbourne revealed that less than 90
per cent of letters were delivered according to the schedule.
Herald-Sun staff posted 59 letters before the advertised...
Campbell Fuller, Herald-Sun, 25 November 1992.
Is the author justified in disputing Australia Post's claim that 96% of letters are delivered on time?