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© 2014 Pacific Crest
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we need 383 wheels in our sample. If we want to reduce it to 1 percent we need to
measure more than 8,000 wheels!
A
re You Ready?
Before continuing, you should be able to ...
I can...
OR
Here’s my question...
explain why utilizing a sample from a
population is more effective than using
the entire population
identify issues that will arise from
collecting a sample instead of using a
population
explain when and why we may choose
to use a nonprobability sample versus a
probability sample.
explain how the sample size relates to the
accuracy of your sampling distribution.
P
lan
How to complete the activity
1. Review the Methodology for Deciding on a Sampling Procedure.
2. Read the Research Notes containing different sampling scenarios (Research Notes 5.2 through 5.5).
3. Read the “Guidelines for Choosing Type of Probability Sample Design” from
Sampling Essentials.
4. Use the Sample Planning Wizard to examine the effects of decreasing margin of error on sample size
and cost. Complete the table available in the Model.
5. Answer the Critical Thinking Questions.
6. Complete the remainder of this activity (from Demonstrate Your Understanding through Assessing
Your Performance) on your own, or as directed by your instructor.
M
odel(s)
Exemplars and representations
T
he
C
ost of
A
ccuracy
We would like our inference to be as accurate as possible, but at what cost? To examine this, let’s take
a sample from a population of 1000 people and conduct a one-hour survey with each participant. The
cost of conducting the survey is $10/hr (the hourly wage you pay your surveyor). There are no overhead
costs. Our goal is to make an inference regarding a mean that has a population standard deviation of 1
unit.
3.4 Sampling