Highway engineers in Ohio are painting white stripes on a highway. The stripes are supposed to be approximately 10 feet long. However, because of the machine, the operator, and the motion of the vehicle carrying the equipment, considerable variation occurs among the stripe lengths. Engineers claim that the variance of stripes should be less than 16 inches squared. At = .05, use the sample lengths given here from 12 measured stripes (in feet and inches) to test the variance claim. Assume stripe length is normally distributed.

(in feet)

(in inches)

9.85

118.2

9.7

116.4

9.9

118.8

9.5

114

9.15

109.8

10.1

121.2

10

120

9.8

117.6

9.9

118.8

10.3

123.6

10.1

121.2

10.2

122.4

10.The appropriate test for this question is:

a.a Z-test for the true variance of stripe length.

b.a t-test for the true mean of stripe length.

c.a Chi-square test for the true mean of stripe length.

d.a Chi-square test for the true variance of stripe length.