The following table shows the number of people that like a

particular fast food restaurant.

1) What is the probability that a person likes Wendy’s?

2) What is the probability that a person is male?

3. What is the probability that a randomly chosen is male and

likes Burger King?

McDonald’s Burger

King

Wendy’s

Male 20 15 10

Female 20 10 25

EOCT Practice

A spinner has 3 sections, each with different point values and

areas.

- The 1-point section is 2/3 of the area of the spinner.

- The 2-point section is1/4 of the area of the spinner.

- The 3-point section is 1/12 of the area of the spinner.

To the nearest tenth of a point, what is the expected value?

a)0.7

b)1.4

c)2.0

d)6.0

EOCT Practice Greg wrote the numbers 1 through 9 on pieces of paper

and placed them in a hat. He will randomly select one

piece of paper from the hat. He will not replace it. Greg

will then randomly select a second piece of paper from

the hat.

What is the probability that Greg will select a piece of

paper with an odd number on it and then, select one

with an even number on it?

a)20/81

b)5/18

c)9/17

d)19/18

Math I

Today’s Essential Question:

How do we take a random sample,

and what statistics can we find with

the data?

Vocabulary •Population: is a group of

people or objects that you

want information about

•Sample: is a subset of the population being studied

Types of samples

•Self-selected sample: members of a population can volunteer to be in the sample

Self-selected sample

•Examples:

Filling out a survey because you want to.

Calling an 800 number on your receipt to fill out a survey about your experience in the store while you shopped.

Types of samples

•Systematic sample: a RULE is used to select members of a population

Systematic sample •Example:

Selecting every 10th person

Types of samples

•Convenience sample: easy to reach members of a population are selected

Convenience sample

•Example:

Asking the first 10 people that walk through the front door.

Types of samples

•Random sample: each member of a population has an equal chance of being selected

Random sample •Example:

Using a random number generator to select a someone out of the population

Types of samples

•Stratified sample: using a subgroup of the population

Stratified sample •Example:

Looking at the EOCT results of females

Unbiased

vs

Biased

Unbiased

•Unbiased sample: is

representative of the

population you want

information about.

Biased

•Biased sample: a sample

that over represents the

population or under

represents PART of the

population

Unbiased vs Biased

•Example:

You polling people at a pet store if

they are in favor of a local dog

park in the area.

Is this biased or unbiased?

John surveys every fifth person leaving a pet supply store. Of those surveyed, ¾ support the city manager’s proposition to tear down the old library and replace the area with the construction of a new pet park. John plans to write a letter to the editor of the local newspaper about the proposal for the new pet park stating that there is tremendous support from the citizens of the town for constructing a new pet park. a) Can the conclusion John stated be accurately supported? b) Suggest another plan for obtaining a good sample population.

I want to know the average height of students at Druid Hills High School. What would be a good method to find this number without checking every student?

Your school is conducting a survey on a

proposed dress code. The first 20 students

entering the school in the morning are

surveyed. What type of sampling method is

used?

a) Convenience

b) Random

c) Stratified random

d) Systematic

A principal is surveying the parents of his school to

find out if they support extending the school day by

20 minutes. Which of the following methods of

choosing a sample will most likely result in a sample

that is representative of all parents?

a) Surveying all the parents at a parent – teacher

meeting b) Surveying 50 parents of 9th grade students

c) Surveying all the parents who volunteer for a

school fundraiser d) Selecting every 20th name from an alphabetical

list of all parents and surveying those parents.

Which of the following questions is not

potentially biased?

a) Do you prefer creamy macaroni and

cheese or bland rice?

b) Don’t you feel the city is wasting money by

building that new stadium?

c) Do you prefer shopping online or in the

stores?

d)Don’t you agree that the driving age should

be raised to 18 to decrease the number of

accidents?

REVIEW:

MM1D3c. Understand that a random sample is used to improve the chance of selecting a representative sample.

Vocabulary

Survey- a study of one or more characteristics of a group.

Population- the entire group you want information about.

Sample- part of the population.

Biased Question- a question that encourages a particular response.

Example 1. A university is conducting a survey to determine

whether a public library has hours of business that satisfy most of its patrons. At the library, students question every tenth library patron who exits the library. Identify the population and classify the sampling method.

2. Suppose the university students conduct the survey by asking all patrons checking out books to fill out a form and mail it back to the university. Classify the sampling method.

7 Samples

1. Random Sample- every member has an equal chance of being selected.

2. Stratified Random Sample- population is divided into distinct groups. Members are selected at random from each group.

3. Systematic Sample- a rule is used to select members.

4. Convenience Sample- only members who are easily accessible are selected.

5. Self-selected Sample- members select themselves by volunteering.

6. Representative Sample- a sample that accurately reflects the characteristics of a population.

7. Biased Sample- a sample that is not representative of the population.

Example 3. Suppose the university students question 20

library patrons chosen at random on a Monday morning between 9:00am and 11:00am. Is this method likely to result in a representative sample or a biased sample? Explain.

Example

4. Tell whether the question is potentially biased. Explain your answer. If the question is potentially biased, rewrite it so that it is not.

a. Because there is a lack of affordable entertainment for teenagers in the city, do you think the city should sponsor more youth activities?

b. Do you think the city should risk an increase in taxes by allowing a new elementary school to be built?

Example

5. In a survey about the need to improve driver safety, 50

randomly selected adults at a senior-citizen resident facility

were asked, “Do you think driver safety would improve if

drivers were required to pass a driving test every ten years

when renewing a driver’s license?”

a. Is the sampling method likely to result in a representative sample or a biased sample? Why?

b. Is the question potentially biased? Explain?

Homework

Textbook

Pg. 361 #1-11