Download Normal Distributions REVIEW Name: Hr:___ Find the average and

Normal Distributions REVIEW
Name: _________________________ Hr:___
1) Find the average and standard deviation for the following:
a) 1, 2, 3, 4, 5, 6, 7, 8
b) 2, 4, 6, 8, 10, 12
c) 12, 20, 15, 17, 19, 13, 15, 18, 21
2) The systolic blood pressures of adults are normally distributed with a mean of 128.4 and a standard
deviation of 19.6
a) Sketch the normal curve for the blood pressures:
b) Give the interval in which blood pressures are approximately 68% of the population.
c) Give the interval in which 95% of the population falls
d) Give the interval in which 99.7% of the population falls
e) What is the percent of blood pressures above 148
f) What is the percent of blood pressures below 89.2
3) The heights of a certain population of males are normally distributed with a mean of 69 inches and a
standard deviation of 6.5 inches.
a) Sketch this distribution.
b) Shade in the curve of the population whose height is less than 82 inches.
c) Approximate the proportion of this population whose height is less than 82 inches.
4) The scores on a particular job aptitude test are normal with an average of 400 and a standard deviation of
100.
a) Sketch this distribution.
b) Shade the curve of the proportion of the population who scored in the top 2.5%
c) If a company will only consider those applicants scoring in the top 2.5%, what scores will they
consider?
5) The score on a scholastic achievement test were normally distributed with a mean of 520 and standard
deviation of 94. If your score was 708, by how many standard deviations did it exceed the average score?
6) The time to complete a certain loan application form is an average of 90 minutes with a standard deviation
of 15 minutes.
a) Sketch this distribution:
b) What are the chances that the loan will take Less than 75 minutes?
c) What are the chances that the loan will take Between 90 and 120 minutes?
d) What are the chances that the loan will take More than 135 minutes?
7) The number of hours that the students in an Intro to Stats class watch the USA network (for NCIS and
House reruns of course) in a week is normally distributed with an average of 9 hours with a standard
deviation of 2.5 hours.
a) Sketch the normal curve:
b) What percent of the students watch more than 11.5 hours of the USA network?
c) What percent of the students watch between 4 to 14 hours of the USA network?
d) One student watches 16.5 hours of the USA network a week. How many standard deviations over the
average are they?
8) In a normal distribution,
a) what percent of the data lies within 1 standard deviation of the mean?
b) what percent of the data lies within 2 standard deviations of the mean?
c) what percent of the data lies within 3 standard deviations of the mean?
9) List 4 properties of all normal curves:
a)
b)
c)
d)
10) Draw a curve that best represents each histogram below and then describe the shape (approx. normal, skewed left,
or skewed right).
a)
b)