6. A corporation is interested in estimating the total earnings from sales of colour television sets at the end of a 3-month period. The total earnings figures are available for all districts within the corporation for the corresponding 3-month period ofthe previous yea r. A simple random sample of 13 district offices is selected from the 123 offices within the corporation. (a) Estimate the current mean earnings My using the 1) ordinary method or 2) ratio estimation that based on the sample. Place a bound on the error of estimation with 95% confidence level. (b) Use a ratio estimator to estimate \"ry , and place a bound on the error of estimation with 95% confidence level. Use the data in the table and take Ix = 128,200. (c) Use a regression estimator to estimate the mean earnings p), , and place a bound on the error of estimation with 95% confidence level. Compare your answer with that in part (a). Are there any advantages in using the regression estimator? Office Three-month data from Three-month data from previous year at current year, yi I i 1 550 2 720 620 980 610 780 - 1600 - 1030 - 1050 \" \