SAMPLING METHODS
Honors
Advanced
Algebra
Presentation
1-3
ESSENTIAL QUESTION AND STANDARDS
EQ: How do I determine if my sampling
method is unbiased?
MCC9-12.S.IC.3 Recognize the purposes of
and differences among sample surveys,
experiments, and observational studies;
explain how randomization relates to each
VOCABULARY
 Sample – a portion of the population.
 Population – the entire group that is being
studied.
 Statistic – a number that describes a sample.
 Parameter – a number that describes the
population.
 Survey – a study of a sample of the population
used to predict characteristics of the entire
population.
 Census – a study of the entire population.
BIASED VS UNBIASED SAMPLES
 Unbiased sample - a random sample that is
representative of the population.
 Underrepresented sample – a sample where one or
more groups of the population are omitted.
 Overrepresented sample – a sample where one or
more groups has a greater representation than in
the general population.
T YPES OF SAMPLES
Name: Random Sample
Method: Every member of the population has an
equal likelihood of being chosen.
Examples: Assign everyone a number and have a
random number generator pick numbers.
OR
Put every person’s name in a hat and pick out
names.
T YPES OF SAMPLES
Name: Systematic Sample
Method: Pick sample participants based on a rule.
Examples: Choose every 5 th person who walks
through the door.
OR
Ask everyone whose last name begins with M.
T YPES OF SAMPLES
Name: Convenience Sample
Method: Pick sample participants based on who is
available.
Examples: Choose the first 10 people you see when
you enter your next class.
OR
Choose the friends that you are meeting after
school.
T YPES OF SAMPLES
Name: Self-Selected Sample
Method: Participants choose to be included in the
sample
Examples: Put out a survey at the front desk for
guests to fill out.
OR
Offer shoppers a discount for going online to answer
a survey.
T YPES OF SAMPLES
Name: Stratified Random Sample
Method: The population is divided into groups. Each
member of each group has an equal chance of being
chosen.
Examples: Choose 10 males and 10 females to
participate.
OR
Choose 20 people born in each decade from 1950 2009.
SAMPLE OR POPULATION?
 What is the population and what is the sample?
A car factory just manufactured a load of 6,000 cars. The
quality control team randomly chooses 60 cars and tests the
air conditioners. They discover that 2 of the air conditioners
do not work .
Population: 6,000 cars
Sample: 60 cars
SAMPLE OR POPULATION?
 What is the population and what is the sample?
In a survey of 40 employees at a company, 18 said they were
unhappy with their pay. The company has 180 employees.
Population: 180 employees
Sample: 40 employees
BIASED OR UNBIASED?
T YPE OF SAMPLE?
 Call 100 random people listed in the phone book to ask how long
Biased
they’ve been living in their home:
,
Random Sample
Ask every 10th person at a school off of a complete roster about
Unbiased
how many courses they are taking:
,
Systematic Sample
Ask 25 families eating at a restaurant on a Tuesday night about
how often they eat out:
,
Biased
Convenience Sample
Out of each class at school, ask a number of students
proportional to the number of students in each class how much
they enjoyed homecoming:
Unbiased
, Stratified Random Sample
HOMEWORK
Pg. 20-21, #14-25