Transcript Presentation Title

Statistical Sampling
Part II – Language and
Technique
This video is designed to accompany
pages 41-76
in
Making Sense of Uncertainty
Activities for Teaching Statistical Reasoning
Van-Griner Publishing Company
Basic Language
List of Individuals
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12
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Sample - Subject/items
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10
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4
6
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that you are able to
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measure/interview.
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7
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11
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Chosen from
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population.
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Population - Larger collection of
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subjects/items that you are interested
in understanding something about.
Critical Distinction
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10
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Remember S-S
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9
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Sample
Statistic – number that describes
the sample. E.g. observed
proportion in sample who answered
“Yes”
Remember P-P
Population
Parameter – number that describes the population.
E.g. true proportion of all U.K. students who would
answer “Yes” to “Do you support gay marriage?”
Identification of Terms
Americans and Their Guns
Parameter - true, unknown percentage
of ALL Americans who would have said
they supported stricter gun laws, if all
had been asked.
Title:
Poll: MajorityPopulation
of Americans Back Stricter Gun Laws
Authors: Sarah Dutton, Jennifer De Pinto, Anthony Salvanto, Fred Backus, Leigh Ann
(All Americans)
Caldwell
Statistic
Source: CBS News January 17, 2013
As the president outlined sweeping new proposals aimed to reduce gun violence, a new
CBS News/New York Times poll found that Americans back the central components of
the president's proposals, including background checks, a national gun sale database,
limits on high capacity magazines and a ban on semi-automatic weapons. Asked if they
generally back stricter gun laws, more than half of respondents - 54 percent - support
stricter gun laws …. That is a jump from April - before the Newtown and Aurora
shootings - when only 39 percent backed stricter gun laws but about the same as ten
years ago.
…
This poll was conducted by telephone from January 11-15, 2013 among 1,110 adults
nationwide. Phone numbers were dialed from samples of both standard land-line and
cell phones. The error due to sampling for results based onSample
the entire sample could be
plus or minus three percentage points.
Simple Random Sampling
A simple random sample (SRS) of size n
consists of n individuals chosen from the
population in such a way that every set of n
individuals had the same chance of being chosen.
Practical Selection Tool
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11
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SRS of size n from N subjects?
1. Label objects 1 to N
2. Use http://www.randomizer.org
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Subtle and Critical
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Keys to confidence in your
parameter estimate?
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1.
The probabilistic nature of the
sample selection
2.
Some really neat mathematics
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Common Confusion
A “fair” sample in a probabilistic
sense is NOT a cross-sectional
sample.
One of least understood, but
most critical interpretations of
what it means to sample “fairly.”
One-Sentence Reflection
A probabilistic sample like an SRS is a
critical step in estimating a population
parameter with a sample statistic.