Create a 85% confidence interval for a population mean from a sample of size 65 with sample mean x = 11.7. The population standard deviation is known to be o = 3.28.

Suppose that the population standard deviation of a student's score is 20. Choose a sample size so that the resulting 95% confidence interval for the population mean score has a margin of error no larger than 5.

A simple random sample of size 23 has mean x̄ = 1.48 and standard deviation s = 1.32. The population is approximately normally distributed. Construct a 99% confidence interval for the population mean

An agricultural researcher plants 14 plots with a new variety of corn. The average yield for these plots is X = 155 bushels per acre. Assume that the yield per acre for new variety of corn follows a normal distribution with unknown mean and a calculated sample standard deviation s = 10 bushels. A 90% confidence interval for the unknown mean is

A ecologist wishes to estimate the mean lifespan for a specific species of bird. Assume that bird lifespan is normally distributed and that each bird's lifespan is independent of all others. The researcher analyzes a random sample of n=7 deceased birds to find out how long they lived for. It is found that the mean lifespan in the sample is y= 5 4 years with standard deviation s=13 years. Choose the correct formula for a 95% confidence interval for the true mean lifespan. X± to.975,n O xt to.975,n-1 n-1 O none of these X+ Z0.975 O x+ to.975,n-1' O xt to.975,n-15

A sample of 120 students yielded a sample mean GPA of 3.35, end a sample standard deviation equal to 0.28. Calculate the 95% confidence interval for the population mean GPA.

A random sample of 9 observations from a normally distributed population produced a mean x̅ =12.4 and a standard deviation s= 2.8. find a 99% confidence interval for the population mean?