5 The lengths of Western bluebirds are normally distributed with mean 16.5 cm and standard deviation 0.6 cm .
A random sample of 150 of these birds is selected.
- How many of these 150 birds would you expect to have length between 15.4 cm and 16.8 cm ?
The lengths of Eastern bluebirds are normally distributed with mean 18.4 cm and standard deviation \(\sigma \mathrm { cm }\). It is known that \(72 \%\) of Eastern bluebirds have length greater than 17.1 cm . - Find the value of \(\sigma\).
A random sample of 120 Eastern bluebirds is chosen. - Use an approximation to find the probability that fewer than 80 of these 120 bluebirds have length greater than 17.1 cm .