other sampling methods lecture 8 sections 2.6 – 2.7 tue, jan 29, 2008
TRANSCRIPT
![Page 1: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/1.jpg)
Other Sampling Methods
Lecture 8
Sections 2.6 – 2.7
Tue, Jan 29, 2008
![Page 2: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/2.jpg)
Stratified Random Sampling Stratified random sample
![Page 3: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/3.jpg)
Stratified Random Sampling Normally the members within each stratum
share a common characteristic that they do not share with members of the other strata.
That is, each stratum is homogeneous.Male vs. female.Resident vs. non-resident.
![Page 4: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/4.jpg)
Stratified Random Sampling
The population
![Page 5: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/5.jpg)
Stratified Random Sampling
The population
The strata
![Page 6: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/6.jpg)
Stratified Random Sampling
The population
One stratum
![Page 7: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/7.jpg)
Stratified Random Sampling
The population
One stratum
Anotherstratum
![Page 8: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/8.jpg)
Stratified Random Sampling
The population
A simple random samplefrom this stratum
![Page 9: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/9.jpg)
Stratified Random Sampling
The population
A simple randomsample fromthis stratum
A simple random samplefrom this stratum
![Page 10: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/10.jpg)
Stratified Random Sampling
The population
Simple random samples from all strata
![Page 11: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/11.jpg)
Stratified Random Sampling
The population
The stratified random sample
![Page 12: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/12.jpg)
Example
Let the population consist of males Andy, Bob, Charlie, Don, Ed, Fred, Greg, and Hank and females Pam, Queeny, Rachel, Susie, Terri, Uzi, Valerie, and Wendy.
Choose a stratified sample of size n = 8, where the strata are the two sexes.
Is the sample representative with regard to sex?
![Page 13: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/13.jpg)
Why Stratified Samples?
If we know the proportion of the population that each group comprises, then we increase our chances of getting a representative sample by using a stratified sample.
![Page 14: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/14.jpg)
Strata vs. Populations
We may be genuinely interested in the differences among the strata.For example, pollsters studying elections
routinely categorize their samples by gender, and ethnic group, party affiliation, etc.
However, in that case, the strata are better viewed as distinct populations.
![Page 15: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/15.jpg)
Cluster Sampling
Cluster Sampling
![Page 16: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/16.jpg)
Cluster Sampling
Note that it is the clusters that are selected at random, not the individuals.
It is hoped that each cluster by itself is representative of the population, i.e., each cluster is heterogeneous.
![Page 17: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/17.jpg)
Cluster Random Sampling
The population
![Page 18: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/18.jpg)
Cluster Random Sampling
The population
The clusters
![Page 19: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/19.jpg)
Cluster Random Sampling
The population
One cluster
![Page 20: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/20.jpg)
Cluster Random Sampling
The population
One cluster
Anothercluster
![Page 21: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/21.jpg)
Cluster Random Sampling
The population
A random sampleof clustersSelect all of these
And all of these
![Page 22: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/22.jpg)
Cluster Random Sampling
The population
The cluster random sample
![Page 23: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/23.jpg)
Example
Now suppose thatAndy, Bob, Pam, and Queeny live in
Fredericksburg.Charlie, Don, Rachel, and Susie live in
Richmond.Ed, Fred, Terri, and Uzi live in Charlottesville.Greg, Hank, Valerie, and Wendy live in
Roanoke.
![Page 24: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/24.jpg)
Example
Use cluster sampling to choose a sample of size n = 8, where the clusters are the cities.
Is the sample representative with regard to sex?
Is the sample representative with regard to geographic location?
![Page 25: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/25.jpg)
Stratified Sampling vs. Cluster Sampling In stratified sampling
From all of the strata we take randomly selected individuals.
In cluster samplingFrom randomly selected clusters we take all
of the individuals.
![Page 26: Other Sampling Methods Lecture 8 Sections 2.6 – 2.7 Tue, Jan 29, 2008](https://reader030.vdocuments.us/reader030/viewer/2022032607/56649ed45503460f94be461d/html5/thumbnails/26.jpg)
Stratified Sampling vs. Cluster Sampling It is done this way because In stratified sampling, the members of a
stratum have some characteristic in common (homogeneous).
In cluster sampling, the members of each cluster are believed to resemble the entire population (heterogeneous).