A random sample of 64 students at a university showed an average age of 25 years and a sample standard deviation of 2 years. The 98% confidence interval for the true average age of all students in the university is

The speed of greyhounds is normally distributed with a standard deviation of 0.15 mph. How many dogs do we need in our sample to estimate the mean speed of all greyhounds to within 0.05 mph for a 95% confidence interval? 35 greyhounds 87 greyhounds 61 greyhounds 42 greyhounds

.A study of 100 patients with back pain reported that the mean duration of pain was 12 months. It is known that the standard deviation of duration of back pain is 6.8 months. Assuming that the duration of this problem is normally distributed in the population; determine a 95% confidence interval for the mean duration of back pain in the population.

In a simple random sample of 144 households in a county in Virginia, the average number of children in these households was 3.62 children. The standard deviation from this sample was 2.40 children. A 90% confidence interval for the mean number of children in all households in this county is?