Statistics released by the National Highway Traffic Safety C

Statistics released by the National Highway Traffic Safety Commission show that on a average weekend night, 1 out of every 10 drivers on the road is drank. If 400 drivers are randomly checked next Saturday night, find the probability that the number of drunk drivers will be more than 35.

Solution

10.

We first get the z score for the critical value:          
          
x = critical value =    35.5      
u = mean = np =    40      
          
s = standard deviation = sqrt(np(1-p)) =    6      
          
Thus, the corresponding z score is          
          
z = (x-u)/s =    -0.75      
          
Thus, the left tailed area is          
          
P(z <   -0.75   ) =    0.773372648 [ANSWER]