Author Question: Use the properties of the standard normal curve to describe the method of finding the area to the ... (Read 33 times)

tingc95 · **on:** Jun 24, 2018

Use the properties of the standard normal curve to describe the method of finding the area to the right of z = 1.42.

Question 2

Your statistics instructor wants you to determine a confidence interval estimate for the mean test score for the next exam. In the past, the test scores have been normally distributed with a mean of 74.2 and a standard deviation of 30.9 . A 95 confidence interval estimate if your class has 30 students is:
a. 68.72 to 79.68.
b. 13.64 to 134.76.
c. 64.92 to 83.48.
d. 62.66 to 85.73.
e. 63.14 to 85.26.

sylvia · **Reply #1 on:** Jun 24, 2018

Answer to Question 1

Since the standard normal table in text gives areas between 0 and positive values of z, to find the area to the right of a z value requires the use of the symmetry property which places .5 of the whole area to the right of z = 0 . Trace down the left most column to the value 1.4 and across the row to the column headed by the value .02. The value is 0.4222, which is the area between z = 0 and z = 1.42 . Subtract this area from 0.5 to obtain the desired area of 0.0778.

Answer to Question 2

E