31.Do the following data indicate that the variance of the population from which this sample has been drawn is significantly more than 12? Use ? = 0.05.
32.A sample of ten earnings per share estimates is shown below.
Use Excel to estimate the variance with a 95% level of confidence.
33.The time it takes to complete a test was recorded for a sample of 15 students. The results follow.
Use Excel to estimate the variance with a 90% level of confidence.
34.A professor believes the variability in time to complete tests has increased. In the past, the variance in minutes to complete a particular test was 25. The time it takes to complete a test was recorded for a sample of 15 students. The results follow.
Use Excel to determine if the variance in times has increased. Use a .02 level of significance.
35.A manufacturing company is considering changing suppliers of a particular raw material. The standard deviation of days until delivery for the current supplier is 3. A sample of 5 delivery times is taken from the new supplier. The data follow:
The manufacturing company will use the new supplier if the variance in delivery time is less than that of the current supplier. Use Excel to determine whether the company should use the new supplier? Use a 10% level of significance.