SOLUTION: Can someone please help? The distribution of a sample of the outside diameters of PVC gas pipes approximates a symmetrical, bell-shaped distribution. The arithmetic mean is 11.0 i

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Question 857579: Can someone please help?
The distribution of a sample of the outside diameters of PVC gas pipes approximates a symmetrical, bell-shaped distribution. The arithmetic mean is 11.0 inches, and the standard deviation is 2.0 inches. About 68 percent of the outside diameters lie between what two amounts?

8.5 and 12.0 inches
12.0 and 13.0 inches
10.0 and 12.5 inches
9.0 and 13.0 inches
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
68% would be +/-1 standard deviation or +/- 2.0 inches.
(11-2,11+2)=(9,13)