CHAPTER 7 CONTINUOUS PROBABILITY DISTRIBUTIONS QUESTIONS WITH ANSWERS.

CHAPTER 7 CONTINUOUS PROBABILITY
DISTRIBUTIONS QUESTIONS WITH
ANSWERS.
Applicants for graduate school take a test that has scores which are normally distributed with a mean of
560 and a standard deviation of 90. What is the probability that a randomly chosen applicant will score
between 550 and 650? ANSWER : -0.3851




Reason:

z=(550-560)/90=-0.11; z=(650-560)/90=1.00. Use Excel function Normdist or z-tables (0.3413+0.0438).



What percentage of the area under a normal curve is within 1, 2, and 3 standard deviations of the
mean? Match the probabilities to the range for the Empirical Rule for the Normal distribution. ANSWER
: -Approximately 68% ↔ μ ± σ


Approximately 95% ↔ μ ± 2σ



Approximately 99.7% ↔ μ ± 3σ



Scores on a graduate school entrance exam follow a normal distribution with a mean of 560 and a
standard deviation of 90. What is the probability that a randomly chosen test taker will score between
560 and 640? ANSWER : -0.3133



Reason:

z=(640-560)/90=0.89. Use Excel function Normdist or z-tables (0.3133).



A graduate school entrance exam has scores that are normally distributed with a mean of 560 and a
standard deviation of 90. What percentage of examinees will score between 400 and 500? ANSWER : -
0.2139