Question

Studies show that gasoline use for compact cars sold in the US is normally distributed with a mean of 25.5 miles per gallon (mpg) and a standard deviation of 4.5 mpg. What percentage of compacts get 30 mpg or more?

Answer 1

Solution :

Given that ,

mean = = 25.5

standard deviation = = 4.5

P(x 30) = 1 - P(x   30)

= 1 - P[(x - ) / (30 - 25.5) / 4.5]

= 1 -  P(z 1)  

= 1 - 0.8413

= 0.1587

Answer = 15.87%