 20 minutes to complete Assignment #1.10, pgs 10-11 [#s 1-13 all]
 Pass back papers
 Check in A#1.10
 Work on completing definitions sheet for Section 1.2, pages 12 –17
 Begin discussion on Sampling Techniques
Section 1.2
Random Samples * Sampling Techniques
Bell Ringer Worksheet – Review from Sec. 1.1
Notes & Assignment – Section 1.2
 Explain the importance of random samples
 Describe the following samplings:
 Stratified
 Cluster
 Systematic
 Multistage
 Convenience
 Construct a simple random sample using random numbers
 Simulate a random process
Use your handout and textbook (pages 12 –
17) and write out the definitions.
 Read pg. 12
A simple random sample of n measurements from a
population is a subset of the population selected in a
manner such that every sample of size n from the population
has an equal chance of being selected.
 Important to remember:
 One of the most important sampling techniques
 Not only does every sample of the specified size have an equal
chance of being selected, but also every individual of the
population has an equal chance of being selected.
 SRS video explanation
 Guided Exercise #3 on page 12.
WEDNESDAY, SEPT 11
PATRIOT’S DAY
 Calculator Pre-Test
 Finish notes and discussion of section 1.2 (Random Samples)
 Begin Assignment for section 1.2
 Assignment:
 - Due Thursday (9/12): Pages 17-18 [#s 1 - 10]
 - QUIZ FRIDAY (9/13), Sections 1.1 - 1.2
1. Number all members of the population sequentially.
2. Use a table, calculator, or computer to select
random numbers from the numbers assigned to the
population members.
3. Create the sample by using population members
with numbers corresponding to those randomly
selected.
A numerical facsimile or representation of a real-world phenomenon.
Simulations are useful in the study of:
 Nuclear Reactors
 Shipbuilding
 Cloud Formation
 Airplane Design
 Medical Science
 War Games
 Highway Design
 Economics
 Production Control
 Electronics
 Although a number is selected for a sample, it is not
removed from the population.
 Simulations often use this.
 Strata: groups or classes within a population that
share a common characteristic.
 Plural of stratum
Characteristics
can be age,
income,
education level,
etc.
1. Number all members of a population
sequentially.
2. Then, from a starting point selected at random,
include every kth member of the population in
the sample.
Advantage: easy to get
Problems: If the population is repetitive or cyclic
in nature, do not use this sampling technique.
 Used by government agencies and certain private research
organizations
1. Begin by dividing the demographic area into sections.
2. Randomly select sections or clusters.
3. Every member of the cluster is included in the sample.
 Used when population is very large or geographically
spread out.
 This method uses a variety of sampling methods to create
successfully smaller groups at each stage.
 The final sample consists of clusters.
 Uses results or data that are conveniently and readily
obtained.
 Runs the risk of being severely biased.
 The list of individuals from which a sample is
actually selected.
 Best case is that it includes the entire population
 Undercoverage happens when a sample frame does
not match the population.
 The difference between measurements from a sample and
corresponding measurements from the respective
population.
 It is caused by the fact that the sample does not perfectly
represent the population.
 THESE ARE NOT MISTAKES!
 The result of poor sample design, sloppy data collection,
faulty measuring instruments, bias in questionnaires, etc.
A#1.2
Pages 17 – 18 #s 1 – 9 all – DUE THURS
QUIZ ON FRIDAY, Sections 1.1 – 1.2