SOLUTION: the average retail price of gasoline (all types) for 2014 was $3.42 cents. what would the standard deviation have to be in order for there to be a 15% probability that a gallon cos

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Question 1150405: the average retail price of gasoline (all types) for 2014 was $3.42 cents. what would the standard deviation have to be in order for there to be a 15% probability that a gallon cost less than $3.00?
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
z=(x-mean)/sd
z=-1.04 for 15th percentile
-1.04=(3.00-3.42)/sd
-1.04 sd=-0.42
sd=$0.40 or 40 cents