Transcript SAMPLE - Cloudfront.net

Understanding
Sampling
Lesson 3-5
Pg. # 100-101
CA Content Standards
» Statistics, Data Analysis, and Probability 2.1:
I can compare different samples of a population with
data from the entire population and identify a
situation in which it makes sense to use a sample.
» Statistics, Data Analysis, and Probability 2.4***:
I can identify data that represent sampling errors and
explain why the sample might be biased.
Vocabulary:
POPULATION
» The entire group of individuals or items
you wish to study.
» A sample is chosen from a population.
Objective
» Understand how sampling is used to
describe group tendencies.
» Math Link: You know how to organize
data and find measures of central
tendency. Now you will learn how
sampling is used to collect data in
real-life situations.
» Tendency: a characteristic or likelihood.
Vocabulary:
POPULATION
» The entire group of individuals or items
you wish to study.
» A sample is chosen from a population.
Vocabulary: SAMPLE
» A selected part of a large group, or
population.
movie
Example 1.
» Jerome sells pets and supplies. He has
a large barrel filled with marbles that
people buy to decorate their aquariums.
The marbles are various colors, all
mixed together. He wonders what
percent of the marbles are green.
» It does not make sense for Jerome to count
all the marbles, so Jerome decided to study
two samples, or parts, of the population.
Remember, the population in a statistical
study is the entire group of people or things
being considered. In this case, the
population is the entire barrel of marbles.
Sample 1.
» Jerome scooped out a bucket of marbles to
test. He counted 200 marbles in the
bucket, 50 of which were green.
50 = 1 = 25%
200
4
About 25% of the marbles in the bucket were
green.
Sample 2.
» Jerome scooped out another bucket of marbles
to test. This time he scooped out 180 marbles,
60 of which were green.
60 = 1 = 33%
180
3
About 33% of the marbles in the second bucket
were green.
Since Jerome’s two estimates gave results of 25%
and 33%, he estimated that about 30% of
marbles in the barrel are green.
Example 2.
»
In each situation, would it make more sense to
study the entire population or a sample?
A. David got a new shipment of doggie treats. Each
small bag is supposed to contain pieces of real
beef jerky. David wants to know the average
number of pieces of beef jerky per bag.
It would take too much time to examine every bag.
Also, after David cuts open a bag of treats, he
can no longer sell it. It makes more sense to
study a sample.
Example 2.
»
In each situation, would it make more sense to
study the entire population or a sample?
B. Kristen wants to know the average height of her
cat’s new kittens.
It is not difficult to measure each kitten. So, it makes
more sense to study the entire population.
When you interpret statistical data, it is important to
know whether the statistics are based on a
sample or on the entire population.
Example 3.
»
The table below shows the results of a 1999 poll of 500
dog owners in a large city. [1] Identify the population being
studied. [2] Then, tell whether the statistics were drawn
from a sample or from the entire population.
Dog Owners
Breed
»
Percent
Beagle
35%
German Shepherd
Retriever
Other
30%
25%
10%
» [1] The population is all dog owners in the city.
[2] The statistics were drawn from a sample, since not all
dog owners were interviewed.
The Moral of the Story:
» Studying the characteristics of a sample
is a way to learn about the whole
population. It is necessary to use a
sample when it is impossible to study
the entire population.
Name Statistics
Name Statistics