7 Previous records have shown that the number of cars entering Bampor on any day has mean 352 and variance 121.
- Find the probability that the mean number of cars entering Bampor during a random sample of 200 days is more than 354 .
- State, with a reason, whether it was necessary to assume that the number of cars entering Bampor on any day has a normal distribution in order to find the probability in part (i).
- It is thought that the population mean may recently have changed. The number of cars entering Bampor during the day was recorded for each of a random sample of 50 days and the sample mean was found to be 356 . Assuming that the variance is unchanged, test at the \(5 \%\) significance level whether the population mean is still 352 .