385 n 8.1
Estimating u with Large Samples
Nordstrom, Circuit City, Dillards, JCPenney, Sears, Wal-Mart, Office Depot, and
Toys 'I' Us are included.
2.9
8.1
-1.9
2.6
4.4
6.5
4.2
6.0
8.9
8.7
8.1
6.1
4.8
2.9
11.9
8.2
-6.0
1.5
6.4
4.7
5.5
4.8
3.0
4.3
9.4
5.5
-1.7
5.8
4.7
6.2
5.1
4.2
15.0
4.1
3.7
(a) Use a calculator with mean and sample standard deviation keys to verify that,
for the preceding data, z = 5.1 and s = 3.8.
(b) Let us say that the preceding data are representative of the entire sector of retail
sales companies. Find an 80% confidence interval for
M the average annual
profit per employee for retail sales.
ولا