3 The time taken in minutes for a certain daily train journey has a normal distribution with standard deviation 5.8. For a random sample of 20 days the journey times were noted and the mean journey time was found to be 81.5 minutes.
- Calculate a \(98 \%\) confidence interval for the population mean journey time.
A student was asked for the meaning of this confidence interval. The student replied as follows.
'The times for \(98 \%\) of these journeys are likely to be within the confidence interval.' - Explain briefly whether this statement is true or not.
Two independent 98\% confidence intervals are found. - Given that at least one of these intervals contains the population mean, find the probability that both intervals contain the population mean.