1. Math 227 Elementary Statistics
Sullivan, 4th ed.

2. Copyright of the definitions and examples is reserved to Pearson Education, Inc.. In order to use this PowerPoint presentation, the required textbook for the class is the Fundamentals of Statistics, Informed Decisions Using Data, Michael Sullivan, III, fourth edition.

3. Discrete Probability Distributions
CHAPTER 6
Discrete Probability Distributions

4. Chapter 6.1 Discreet Random Variables
Objective A : Discrete Probability Distribution
Objective B : Mean and Standard Deviation of a Discrete Random Variable
Objective C : Mean Expected Value
Chapter 6.2 Binomial Probability Distribution
Objective A : Criteria for a Binomial Probability Experiment
Objective B : Binomial Formula
Objective C : Binomial Table
Objective D : Mean and Standard Deviation of a Binomial Random Variable
Objective E : Applications

5. Chapter 6.1 Discreet Random Variables
Objective A : Discrete Probability Distribution
A1. Distinguish between Discrete and Continuous Random Variables

6. Example 1: Determine whether the random variable is discrete or continuous. State the possible values of the random variable.
(a) The number of fish caught during the fishing tournament.
Discrete
(b) The distance of a baseball travels in the air after being hit.
Continuous

7. A2. Discrete Probability Distributions

8. Example 1: Determine whether the distribution is a discrete probability distribution. If not, state why.
(a)
0.34 1
0.21 2
0.13 3
0.04 4
0.01
Not a discreet probability distribution because it does not meet

9. (b)
0. 40 1
0.31 2
0.23 3
0.04 4
0.02
It is a discreet probability distribution because it meets

10. Example 2 :
(a) Determine the required value of the missing probability to make the distribution a discrete probability distribution.
(b) Draw a probability histogram.
0. 30 1
0.15 2 ? 3
0.20 4 5
0.05

11. (a) The required value of the missing probability
(b) The probability histogram

12. Chapter 6.1 Discreet Random Variables
Objective A : Discrete Probability Distribution
Objective B : Mean and Standard Deviation of a Discrete Random Variable
Objective C : Mean Expected Value
Chapter 6.2 Binomial Probability Distribution
Objective A : Criteria for a Binomial Probability Experiment
Objective B : Binomial Formula
Objective C : Binomial Table
Objective D : Mean and Standard Deviation of a Binomial Random Variable
Objective E : Applications

13. Chapter 6.1 Discreet Random Variables
Objective B : Mean and Standard Deviation of a Discrete Random Variable

14. Example 1: Find the mean, variance, and standard deviation of the discrete random variable.
(a) Mean
(1)

15. (b) Variance ---> Use the definition formula

16. (c) Variance ---> Use the computation formula
(2b)

17. Chapter 6.1 Discreet Random Variables
Objective A : Discrete Probability Distribution
Objective B : Mean and Standard Deviation of a Discrete Random Variable
Objective C : Mean Expected Value
Chapter 6.2 Binomial Probability Distribution
Objective A : Criteria for a Binomial Probability Experiment
Objective B : Binomial Formula
Objective C : Binomial Table
Objective D : Mean and Standard Deviation of a Binomial Random Variable
Objective E : Applications

18. Chapter 6.1 Discreet Random Variables
Objective C : Mean Expected Value
The mean of a random variable is the expected value, , of the probability experiment in the long run. In game theory is positive for money gained and is negative for money lost.

19. Example 1: A life insurance company sells a $250,000 1-year term life insurance policy to a 20-year-old male for $ According to the National Vital Statistics Report, 56(9), the probability that the male survives the year is Compute and interpret the expected value of this policy to the insurance company.
In the long run, the insurance company will profit $33.50 per 20-year-old male.

20. Example 2: Shawn and Maddie purchase a foreclosed property for $50,000 and spend an additional $27,000 fixing up the property. They feel that they can resell the property for $120,000 with probability 0.15, $100,000 with probability , $80,000 with probability 0.25, and $60,000 with probability Compute and interpret the expected profit for reselling the property.
In the long run, the expected gain is $15,000 per house.

21. Chapter 6.1 Discreet Random Variables
Objective A : Discrete Probability Distribution
Objective B : Mean and Standard Deviation of a Discrete Random Variable
Objective C : Mean Expected Value
Chapter 6.2 Binomial Probability Distribution
Objective A : Criteria for a Binomial Probability Experiment
Objective B : Binomial Formula
Objective C : Binomial Table
Objective D : Mean and Standard Deviation of a Binomial Random Variable
Objective E : Applications

22. Chapter 6.2 Binomial Probability Distribution
Objective A : Criteria for a Binomial Probability Experiment
The binomial probability distribution is a discrete probability distribution that obtained from a binomial experiment.

23. Example 1: Determine which of the following probability experiments represents a binomial experiment. If the probability experiment is not a binomial experiment, state why.
(a) A random sample of 30 cars in a used car lot is obtained, and their mileages recorded.
Not a binomial distribution because the mileage can have more than 2 outcomes.
(b) A poll of 1,200 registered voters is conducted in which the respondents are asked whether they believe Congress should reform Social Security.
A binomial distribution because
– there are 2 outcomes. (should or should not reform Social Security)
– fixed number of trials. (n = 1200)
– the trials are independent.
– we assume the probability of success is the same for each trial of experiment.

24. Chapter 6.1 Discreet Random Variables
Objective A : Discrete Probability Distribution
Objective B : Mean and Standard Deviation of a Discrete Random Variable
Objective C : Mean Expected Value
Chapter 6.2 Binomial Probability Distribution
Objective A : Criteria for a Binomial Probability Experiment
Objective B : Binomial Formula
Objective C : Binomial Table
Objective D : Mean and Standard Deviation of a Binomial Random Variable
Objective E : Applications

25. Chapter 6.2 Binomial Probability Distribution
Objective B : Binomial Formula
Let the random variable be the number of successes in trials of a binomial experiment.

27. Example 1: A binomial probability experiment is conducted with the given parameters. Compute the probability of successes in the independent trials of the experiment.

28. Example 2: According to the 2005 American Community Survey, 43% of women aged 18 to 24 were enrolled in college in Twenty-five women aged 18 to 24 are randomly selected, and the number of enrolled in college is recorded.
(a) Find the probability that exactly 15 of the women are enrolled in college.

29. (b) Find the probability that between 11 and 13 of the women, inclusive, are enrolled in college.

30. Chapter 6.1 Discreet Random Variables
Objective A : Discrete Probability Distribution
Objective B : Mean and Standard Deviation of a Discrete Random Variable
Objective C : Mean Expected Value
Chapter 6.2 Binomial Probability Distribution
Objective A : Criteria for a Binomial Probability Experiment
Objective B : Binomial Formula
Objective C : Binomial Table
Objective D : Mean and Standard Deviation of a Binomial Random Variable
Objective E : Applications

31. Chapter 6.2 Binomial Probability Distribution
Objective C : Binomial Table
Example 1: Use the Binomial Table to find with and .
From Cumulative Binomial Probability Distribution (Table IV),
From Binomial Probability Distribution (Table III),

32. Example 2: According to the American Lung Association, 90% of adult smokers started smoking before turning 21 years old. Ten smokers 21 years old or older are randomly selected, and the number of smokers who started smoking before 21 is recorded.
(a) Explain why this is a binomial experiment.
– There are 2 outcomes (smoke or not)
– The probability of success trial is the same for each trial of experiment
– The trials are independent
– Fixed numbers of trials

33. (b) Use the binomial formula to find the probability that exactly 8 of
them started smoking before 21 years of age.
From Binomial Probability Distribution (Table III),
(c) Use the binomial table to find the probability that at least 8 of them
started smoking before 21 years of age.
From Binomial Probability Distribution (Table III),

34. (d) Use the binomial table to find the probability that between and 9 of them, inclusive, started smoking before 21 years of age.
From Binomial Probability Distribution (Table III),

35. Chapter 6.1 Discreet Random Variables
Objective A : Discrete Probability Distribution
Objective B : Mean and Standard Deviation of a Discrete Random Variable
Objective C : Mean Expected Value
Chapter 6.2 Binomial Probability Distribution
Objective A : Criteria for a Binomial Probability Experiment
Objective B : Binomial Formula
Objective C : Binomial Table
Objective D : Mean and Standard Deviation of a Binomial Random Variable
Objective E : Applications

36. Chapter 6.2 Binomial Probability Distribution
Objective D : Mean and Standard Deviation of a Binomial Random Variable
Example 1: A binomial probability experiment is conducted with the given parameters. Compute the mean and standard deviation of the random variable .

37. Example 2: According to the 2005 American Community Survey, 43% of women aged 18 to 24 were enrolled in college in 2005.
(a) For 500 randomly selected women ages 18 to 24 in 2005, compute the mean and standard deviation of the random variable , the number of women who were enrolled in college.
(b) Interpret the mean.
An average of 215 out of 500 randomly selected women aged 18 to 24 were enrolled in college.

38. (c) Of the 500 randomly selected women, find the interval that would be considered "usual“ for the number of women who were enrolled in college.
Data fall within 2 standard deviations of the mean are considered to be usual.
(d) Would it be unusual if 200 out of the 500 women were enrolled in college? Why?
No, because 200 is within the interval obtained in part (c). It is not unusual to find 200 out of 500 women were enrolled in college in 2005.