Question 1
True or false, areas under the standard normal curve cannot be negative, whereas z-scores can be positive or negative.
◦ True
◦ False
Question 2
Most problems involving normally distributed variables are one of two types.
Type A: Find a probability or percentage, e.g. find the probability that X lies in a specified range.
Type B: Find the observation corresponding to a given probability or percentage.
Suppose that scores on a test are normally distributed with a mean of 80 and a standard deviation of 8. Which of the following questions below are of type B?
a. Find the 80th percentile.
b. Find the cutoff for the A grade if the top 10% get an A.
c. Find the percentage scoring more than 90.
d. Find the score that separates the bottom 30% from the top 70%.
e. Find the probability that a randomly selected student will score more than 80.
◦ a, b, c, d
◦ c, e
◦ b, d
◦ a, b, d