Suppose we are interested in the average net sales (in millions of dollars) for a population of 37 companies that manufacture computer equipment: (1) 42.88 (6) 253.20 (11) 18.99 (16) 90.48 (21) 6.58 (26) 7.30 (31) 29.50 (36) 21.13 (2) 43.36 (7) 103.19 (12) 30.90 (17) 17.33 (22) 8.75 (27) 4.59 (32) 20.52 (37) 29.83 (3 )9.08 (8) 2869.35 (13) 3009.49 (18) 7.96 (23) 39.98 (28) 6.03 (33) 8.43 (4) 40.94 (9) 196. 32 (14) 35.52 (19) 7.94 (24) 17.66 (29) 29.93 (34) 58.08 (5) 80.72 (10) 193.34 (15) 21.22 (20) 5.21 (25) 17.47 (30) 21.64 (35) 35.52 (a) Who is the target population? What are the population units?

(b) What is the variable answer? What is the attribute of the population of interest?

(c) Suppose we decide to make an estimate of the average sales for all companies by selecting a simple random sample of size n = 8, using observations 3, 4, 12, 15, 21, 22, 25, 30. What value do we get for the average of your sample?

(d) Assuming that the net sales of the 37 companies were measured without error, three other types of survey error may be present: coverage error, error of non-response and sampling error. Indicate whether each of the other three types error is present when estimating the mean and explains why.