1. Statistics are Tools!
Statistics – techniques for organizing,
summarizing, and interpreting data
Which “tool” you choose depends on:
What you want to know
What type of data you have
What kind of research design you used
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2. Statistics and Research
Statistics are used to analyze the data
collected in a research study
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3. Descriptive Statistics
Techniques to organize, display, and describe
data using tables, graphs, and summary
measures.
Number Letter % of
Grade Grade Class
90s A 16
80s B 44
70s C 28
60s D 12
100
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4. Inferential Statistics
Techniques that enable us to use information
gathered from a sample to make
decisions, inferences, or predictions about a
population.
Allows statements that go beyond the current
data or information.
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5. Examples of Inferential Statistics
TV networks monitor the popularity of their programs
by hiring Nielsen and other organizations to sample
the preferences of TV viewers.
The accounting department of a large firm will select a
sample of the invoices to check for accuracy for all the
invoices of the company.
Pre-election polling techniques used to predict election
results
“Based on our sample of 10,000 drivers
across the U.S., we estimate that
between 34% to 40% of all U.S. drivers
are driving on underinflated tires.”
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6. Populations and Parameters
Suppose a statistician wanted to know:
Average gpa all students accepted to OLLU
Gross sales at Church’s Fried Chicken stores this
year in San Antonio
Average customer satisfaction rating for all Target
stores in San Antonio
Population is all elements (can be people or
things) whose characteristics are being
studied. Also called the “target population.”
A value (average, total, etc.) that is calculated
from the entire population is called a
parameter.
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7. Samples and Statistics
Recall that the statistician wants to know the
average customer satisfaction rating for all
Target stores in San Antonio.
A survey is given to every 100th customer at 5
randomly selected Target stores in S.A. during a
three day period
A sample is a subset of the population that is
selected for study.
A value that is calculated from a sample is
called a statistic.
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