Use double sampling to estimate the mean or total of a population of your choice in which an auxiliary variable exists that is easier to observe than the variable of interest. In the process of carrying out the survey and making the estimate, think about or discuss with others the following:
(a) What practical problems arise in establishing a frame, such as a map or list of units, from which to select the sample?
(b) How is the sample selection actually carried out?
(c) What special problems arise in observing the units selected?
(d) Estimate the population mean or total using ratio estimation.
(e) Estimate the variance of the estimator above.
(f) Give a 95% confidence interval for the population mean or total.
(g) How would you improve the survey procedure if you were to do it again?