copyright©ed2netlearning.inc1 getting predictions about probability

Copyright©Ed2NetLearning.Inc 1

GETTING PREDICTIONS ABOUT PROBABILITY


PRE-REQUISITE SKILL

Solve each proportion.

1. K = 12

9 54

2. 24 = m

96 24

3. 5 = 30

j 96


MAKING PREDICTIONS - OBJECTIVE

• To predict the actions of a larger group using a sample.


What is a Survey ?

• A Survey is a method of collecting information. The group being studied is the population. Some times the population is very large. To save time and money, part of the group called a sample is surveyed.


Sample

A good sample is • Selected at random, or without preference, • Representative of the population, and• Large enough to provide accurate data.


Determine a Good Sample

Q. Every sixth person entering a stationary store one day is asked to state whether they support the proposed tax for their district. Determine whether the sample is a good sample.

A. i) Asking every sixth person ensures a random survey.

ii) The sample should be a representative of a large population; that is , every person living in the school district.

iii) The sample is large enough to provide accurate information.

So this sample is a good sample.


Determine a good sample

• 250 people at the beach in the summer are asked to name their favorite vacation spot. Is this a good sample, explain.

• No, people at the beach during summer prefer only beach at the vacation spot. So they do not represent a large population.


Now Your Turn

Q. Every seventh person who walked into the school was asked how or she got to school. Determine whether the sample is a good sample.


Predict More!

Q. Miss Candella went to an ice cream shop to conduct a survey. She asked every tenth person who enters into the shop to name his or her favorite dessert. Is this a good sample, explain.


Make Predictions Using Proportions

• Juliet asked every 10th student who walked into school to name their favorite dishes. What is he probability that a student will prefer Chinese dishes?

• P (Chinese) = number of students that like Chinese dishes

number of students surveyed

= 18

32

= 0.5625 = 56%

Favorite dishes

Dishes Students

Chinese 18

American 9

Sausage 3

Indian 2


Making Predictions Using Proportions

• Using the previous table, there are 384 students at the school Juliet attends. Predict how many students prefer Chinese dishes.

• Use a proportion 18 = s

32 384 32 x s = 18 x 384

s = 6912 = 216 32 Of 384 students, 216 students prefer Chinese dishes

S = students who prefer chinese dishes


Now your turn 1. Hardy asked every 6th person in the school cafeteria to name the kind of

activity he or she would like to have for the school’s outing . A) What is the probability that a student will prefer water park? B) There are 408 students at the school Hardy attends. Predict how many students prefer going to water park?

SCHOOL OUTING

OUTING STUDENTS

Amusement park 15

Cricket game 10

Water park 10

Swimming 5


Review

A good sample is • Selected at random, or without preference, • Representative of the population, and• Large enough to provide accurate data.

We can use the results of a survey to predict and estimate the actions of a larger group.


Assessment1. Every 6th student who walked into the school was asked how she came

to school. Determine whether the sample is a good one or not?

2. Every 3rd shopper at a grocery store is asked whether or not he or she owns a pet. Is it a good sample or not?

3. Use the following information and the table shown. Every 10th student entering the school was asked which one of the 4 subjects was his or her favorite.

3. What is the probability that any student prefers science?

4. There are 800 students at the school. Prefer how many students prefer science?

Favorite Subjects

Subjects Students

Arts 2

Mathematics 1

Science 1

Social science 4


Assessment Use the table and the following information:

5. What is the size of the sample?

6. What is the probability that a student will

prefer soccer?

7. What is the probability that a student will prefer

cricket?

8. There are 550 students in the school. Predict

how many students prefer athletics.

9. Every 20th student leaving school is asked where the school should hold the year end outing?

10. If 12 out of 50 people surveyed prefer to watch television after 11 pm, how naby people out of 1000 would prefer to watch tv after 11 pm?

Favorite Sports

Foot ball 8

Base ball 3

Cricket 5

Athletics 4


Great Job!

copyright©ed2netlearning.inc1 getting predictions about probability

Documents

chinese dishes s

large population

good sampleq

p chinese

school district

good sample250 people

school cafeteria

random survey