4) You have an SRS of 22 observations from a large population. The distribution of sample values is roughly symmetric with no outliers. What critical value would you use to obtain a 95% confidence interval for the mean of the population?

1. 2.183
2. 2.189
3. 2.518
4. 2.080

8) Based on a sample of 30 randomly selected years, a 90% confidence interval for the mean annual precipitation in one city is from 45.3 inches to 48.7 inches. Find the margin of error.

9) A coffee manufacturer claims that the mean amount of coffee in its 4ounce jars is 4.0 ounces. Based on a sample of 50 jars, a consumer advocate group obtains the following 99% confidence interval for the population mean weight, :3.95 ounces to 4.05 ounces. Based on this interval, do you think that the manufacturer's claim is plausible? Explain your thinking.

10) A college statistics professor has office hours from 9am to 10:30 am daily. A sample of waiting time to see the professor(in minutes) is

10,12, 20, 15, 17, 10, 30, 28, 35, 28, 19, 27, 25, 22, 33, 37, 14, 21, 20, 23.

Assuming standard deviation is 7.84, find the 95% confidence interval for the population mean.

11.a machine at a soft drink factory is calibrated to dispense 12 ounces of cola into cans. A simple random sample of 41 cans is pulled from the line after being filled and the contents are measured. the mean content of the 41 can is 11.92 ounces with a standard deviation of 0.085 ounces

a. Construct and interpret a 95% confidence interval to estimate the true mean contents of the cans being filled by this machine

B Based on your result from (a), does the machine appear to be working properly? Justify your answer.

12. Weights of women in one age group are normally distributed with a standard deviation of 10 lb. A researcher wishes to estimate the mean weight of all women in this age group. Find how large a sample must be drawn in order to be 90 percent confident that the sample mean will not differ from the population mean by more than 3.4 lb.