collusion, this variance was 16.08. Assume that the data can be regarded as an independent random sample from two normal distributions. 1. Test, at the 5% level, the null hypothesis

Two coworkers commute from the same building. They are interested in whether or not there is any variation in the time it takes them to drive to work. They each record their times for 20 commutes. The first worker's times have a variance of 12.2. The second worker's times have a variance of 16.9. The first worker thinks that he is more consistent with his commute times and that his commute time is shorter. Test the claim at the 10% level.What is the F statistic? (Round your answer to two decimal places.)

A student noticed that when she gets less than 8 hours of sleep at night, she scores lower on her test grades. Can one conclude that this positive correlation shows a causal relationship? OYes, because it is well known that less sleep lowers test scores OYes, because it is not a negative correlation O No, because all students get less than 8 hours of sleep at night No, because it is possible that the student gets lower test grades because of another factor, such as not studying

A set of solar batteries is used in a research satellite. The satellite can run on only one battery, but it runs best if more than one battery is used. The variance ?2 of lifetimes of these batteries affects the useful lifetime of the satellite before it goes dead. If the variance is too small, all the batteries will tend to die at once. Why? If the variance is too large, the batteries are simply not dependable. Why? Engineers have determined that a variance of ?2 = 23 months (squared) is most desirable for these batteries. A random sample of 22 batteries gave a sample variance of 15 months (squared). Using a 0.05 level of significance, test the claim that ?2 = 23 against the claim that ?2 is different from 23. (f) Find a 90% confidence interval for the population variance. (Round your answers to two decimal places.) (g) Find a 90% confidence interval for the population standard deviation. (Round your answers to two decimal places.)