A turn in ©
SALES OF PUBLISHER X
(MILLIONS OF UNITS)
S
4.5
4
REVENUE OF PUBLISHER X
(MILLIONS OF DOLLARS)
28
26
24
22
20
18-
16
14
12
10
8
6
4
'01 02 03 04 05 06 07 08 '09 '10
3.5
3
2.5 -
2
'01 02 03 04 05 06 07 08 09 10
1. What was the approximate difference between the average revenue per unit generated
in 2008 and in 2002?
A. $1.15
B. $1.70
C. $2.50
D. $3.25

Afactory makes propeller drive shafts for ships. a quality assurance engineer at the factory needs to estimate the true mean length of the shafts. she randomly selects four drive shafts made at the factory, measures their lengths, and finds their sample mean to be 1000 mm. the lengths are known to follow a normal distribution whose standard deviation is 2 mm. calculate a 95% confidence interval for the true mean length of the shafts. input your answers for the margin of error, lower bound, and upper bound.