Question 1.103

1.103 Quartiles of Normal distributions.

The median of any Normal distribution is the same as its mean. We can use Normal calculations to find the quartiles for Normal distributions.

  1. What is the area under the standard Normal curve to the left of the first quartile? Use this to find the value of the first quartile for a standard Normal distribution. Find the third quartile similarly.
  2. Your work in part (a) gives the Normal scores for the quartiles of any Normal distribution. What are the quartiles for the lengths of human pregnancies? (Use the distribution given in the previous exercise.)

1.103

(a) The area to the left of the first quartile is 25%. The corresponding is -0.67. The area to the left of the third quartile is 75%. The corresponding is 0.67. (b) For the first quartile, . For the third quartile, .