Download Sampling

Bell Ringer
5-15-17
• In your own words define the
following:
• 1.
• 2.
• 3.
• 4.
• 5.
Convenience
Random
Stratified
Systematic
Cluster
Sampling Methods
(ways to collect data)
Monday, May 15, 2017
Inferential Statistics
•Inferential statistics enables
you to make an educated
guess about a population
parameter based on a statistic
computed from a sample
randomly drawn from that
population.
Sampling
• When conducting a survey,
experiment, or observational study, it
is almost impossible to survey
everyone in a population so people
use various sampling methods to
gather information.
• One major concern about sampling
methods is whether it is a biased or
unbiased method to gather
information.
Sampling Methods
•Convenience sampling:
when those chosen as a
sample of the population are
chosen due to ease of
collecting data.
•SIMPLE EASY (first 5 people)
•NOT a “good” method…
Sampling Methods
• Random sampling:
when everyone in a
population has an
equal chance of being
chosen in the
experiment.
Sampling Methods
Stratified sampling:
when the population is
first divided into similar
categories and the
number of members in
each category is
determined.
Sampling Methods
Systematic sampling: when
you determine a method for
which to choose members of
the population (assign
numbers to the population
and then choose every 5th
person to participate)
Sampling Methods
Cluster sampling: when
you randomly put the
population Into clusters
and then choose a
Cluster randomly and
then randomly choose
people in that cluster to
participate.
Example if selecting 10 animals from 25 dogs, 15 cats, and 10 rabbits
• Random sampling: when everyone in a population has an
equal chance of being chosen in the experiment.
Randomly selecting 10 from all 50 animals
• Stratified sampling: when the population is first divided into
similar categories and the number of members in each
category is determined. Select 5 from 25 dogs, 3 from 15 cats
and 2 from the rabbits
• Systematic sampling: when you determine a method for
which to choose members of the population (assign numbers
to the population and then choose every 5th person to
participate) Give every animal a random number and then
choose every 5th number
• Cluster sampling: when you randomly put the population into
clusters and then choose a cluster randomly and then
randomly choose people in that cluster to participate.
Randomly put the animals into 2 groups of 25, choose a
group, and then choose 10 from that selected group.
Which sampling method is used in
the scenario below?
A Gallop poll surveyed 1,018 adults by
telephone in each region of the country, and
22% of them reported that they smoked
cigarettes within the past week.
A.
B.
C.
D.
Random
Stratified
Systematic
Cluster
Which sampling method is used in
the scenario below?
A principal goes to one classroom in each
department and chooses two students from
each classes to participate in a school climate
survey.
A.
B.
C.
D.
Random
Stratified
Systematic
Cluster
Which sampling method is used in
the scenario below?
WSFCS sends out a survey to parents by
generating a list of student numbers from
PowerSchool.
A.
B.
C.
D.
Random
Stratified
Systematic
Cluster
Biased Questions
• Some questions may use language that people can
associate with emotions:
• How much of your time do you waste on Snap Chat?
• Some questions may refer to a majority or supposed
authority:
• Would you agree with the NCAE that teachers should
be paid more for earning their master’s degree?
• Phrased awkwardly:
• Do you disagree with people who oppose the ban on
smoking in public places?
Sampling Bias
• Sampling Bias occurs when one or more sub
groups of a population are either over represented
or under represented when conducting a survey
or experiment.
• Using the appropriate sampling method for the
question reduces bias.
• Discuss with your partner some examples of bias
that could occur when choosing a sample from a
population.
• Be prepared to share your examples.
Activity:
• Martha wants to construct a survey that shows
which sports students at her school like to play
the most.
• List the goal of the survey.
• What population sample should she interview?
• How should she administer the survey?
• Create a data collection sheet that she can use to
record her results.
What is needed to determine
causation for the population
Random
Selection
Random
Assignment
No Random
Selection
Causality
Causality
Population Only to sample
No Random No causality
Assignment Population
No causality
No results!
Assignments
•Classwork:
Samples & Stats
•Homework:
Sampling Procedures
Practice
Exit Ticket
• In your Math Journal, write a
summary of the past 2 days
lessons. You may write a
paragraph or make a list with
examples. Show your work to
Mrs. Leahy before exiting the
classroom.