A traffic study at one point on an interstate highway shows that vehicle speeds are normally ...

A traffic study at one point on an interstate highway shows that vehicle speeds are normally distributed with a mean of 61.3 mph and a standard deviation of 3.3 mph. If a vehicle is randomly checked, find the probability that its speed is between 55.0 mph and 60.0 mph.

Q. 2

The mean of a normal probability distribution is 400 and the standard deviation is 10 . About 95 of the observations lie between what two values?

Q. 3

Find the value of z(0.73) + z(0.27).

Q. 4

Find the area between z(0.79) and z(0.43).

Q. 5

The mean of a normal probability distribution is 500 and the standard deviation is 10 . About 68 of the observations lie between what two values?

Q. 6

The value of z(0.10) z(0.90) is
 a. 2.56.
  b. -2.56.
  c. 1.28.
  d. -1.28.

Q. 7

The value of z(0.70)  z(0.30) is
 a. 1.04.
  b. -1.04.
  c. 0.52.
  d. -0.52.