SOLUTION: The average retail price of gasoline (all types) for the first half of 2005 was 212.2 cents. What would the standard deviation have to be in order for a 19% probability that a gall

Algebra ->  Probability-and-statistics -> SOLUTION: The average retail price of gasoline (all types) for the first half of 2005 was 212.2 cents. What would the standard deviation have to be in order for a 19% probability that a gall      Log On


   



Question 1081874: The average retail price of gasoline (all types) for the first half of 2005 was 212.2 cents. What would the standard deviation have to be in order for a 19% probability that a gallon of gas costs less than $1.80?
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
19% probability or the 19th percentile is z=-0.88 from the table.
-0.88=(1.80-2.122)/sd
-0.88sd=-0.312
sd=$0.355
15.87% percentile is 1 sd, so this is just under 1 sd.