Statistics
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Data Collection
Summarizing Data
Interpreting Data
Drawing Conclusions from Data
Data Collection
• Designing experiments
– Does aspirin help reduce the risk of heart
attacks?
• Observational studies
– Polls - Clinton’s approval rating
Summarizing and Interpreting Data
• Grade distribution for a college course
• Baseball players batting average against
left-handed pitchers during night games on
artificial turf …
Drawing Conclusions
• Quality control and improvement
• Analysis of designed experiments
• Analysis of observational studies
Population
The set of data (numerical or otherwise)
corresponding to the entire collection of
units about which information is sought
Population Examples
• Unemployment - Status of ALL employable
people (employed, unemployed) in the U.S.
• SAT Scores - Math SAT scores of EVERY
person that took the SAT during 1997
• Responses of ALL currently enrolled
underage college students as to whether
they have consumed alcohol in the last 24
hours
Sample
A subset of the population data that are
actually collected in the course of a study.
Sample Examples
• Unemployment - Status of the 1000
employable people interviewed.
• SAT Scores - Math SAT scores of 20 people
that took the SAT during 1997
• Responses of 538 currently enrolled
underage college students as to whether
they have consumed alcohol in the last 24
hours
Population vs. Sample
Population
Sample
WHO CARES?
In most studies, it is difficult
to obtain information from
the entire population. We
rely on samples to make
estimates or inferences
related to the population.