The waiting times​ (in minutes) of a random sample of 2020 people at a bank have a sample standard deviation of 3.33.3 minutes. Construct a confidence interval for the population variance sigma squaredσ2 and the population standard deviation sigmaσ. Use a 90 %90% level of confidence. Assume the sample is from a normally distributed population.

The mean number of English courses taken in a two-year time period by male and female college students is believed to be about the same. An experiment is conducted and data are collected from 29 males and 16 females. The males took an average of three English courses with a standard deviation of 0.8. The females took an average of four English courses with a standard deviation of 1.0. Are the means statistically the same? (Assume a 5% level of significance.)

The newest model of a car battery from a popular brand is supposed to have a lifetime of  60  months, but the lifetime varies slightly from battery to battery. It is known that the population of all lifetimes (in months) of this model of car battery is approximately normally distributed. You are a product reviewer who wants to estimate the standard deviation for this population with a random sample of  22  car batteries. Follow the steps below to construct a  99%  confidence interval for the population standard deviation of all lifetimes of this model of car battery. (If necessary, consult a list of formulas.) (a)Click on "Take Sample" to see the results from the random sample. Take Sample Number of carbatteries Sample mean Sample standard deviation Sample variance 22 57.16 0.38 0.1444   To find the confidence interval for the population standard deviation, first find the confidence interval for the population variance. Enter…

The president of a large university wishes to compare the standard deviation of the ages of students presently enrolled to previous years. The distribution of ages has been approximately normal. Find the 90% confidence interval for the population standard deviation of the student ages of the University. A random sample of 20 university students has a standard deviation of 6.1 years in a mean of 23.8 years what is the confidence interval of the population standard deviation?

The newest model of a car battery from a popular brand is supposed to have a lifetime of  60  months, but the lifetime varies slightly from battery to battery. It is known that the population of all lifetimes (in months) of this model of car battery is approximately normally distributed. You are a product reviewer who wants to estimate the standard deviation for this population with a random sample of  22  car batteries. Follow the steps below to construct a  99%  confidence interval for the population standard deviation of all lifetimes of this model of car battery. (If necessary, consult a list of formulas.) (a)Click on "Take Sample" to see the results from the random sample. Take Sample Number of carbatteries Sample mean Sample standard deviation Sample variance           To find the confidence interval for the population standard deviation, first find the confidence interval for the population variance. Enter the values…

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 random sample of 32 showed that the mean shoe size for American men is 10.5 with a standard deviation of 1.12. Assuming normality, find the 95% confidence interval for the mean shoe size for American men. A random sample of 32 showed that the mean shoe size for American men is 10.5 with a standard deviation of 1.12. Assuming normality, find the 95% confidence interval for the mean shoe size for American men.  (9.99, 11.01)  (10.112, 10.888)  (10.096, 10.904)  (10.174, 10.826)