A sample of 75 concrete blocks had a mean mass of 38.3 kg with a standard deviation of 0.6 kg.
a) Find a 95% confidence interval for the mean mass of this type of concrete block.
b) Find a 99% confidence interval for the mean mass of this type of concrete block.
c) An engineer claims that the mean mass is between 38.2 and 38.4 kg. With what level of confidence can this statement be made?
d) How many blocks must be sampled so that a 95% confidence interval will specify the mean mass to within ±0.1 kg?
e) How many blocks must be sampled so that a 99% confidence interval will specify the mean mass to within ±0.1 kg?