Lecture 4.pdf


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Lecture 4
Population and sample
Measures of center
What is typical? Measures of center

Population and sample
Cases (individuals) of interest?

Sampling (random)

Population and sample

Population

Inference

sample

Descriptive
statistics

NOTE: Sample should be representative of the population

Examples

A political scientist wants to know what percentage of college-age
adults consider themselves conservatives.

Government economists inquire about average household income.

A market research firm wants to learn what percent of adults aged
18-35 saw television advertisements for a new gas-electric car.

Population data: data from every individual of interest
(are fixed and complete)

Wish information about a large group of individuals (Population)!

Collect information about only part of the group (Sample)

Time, cost, inconvenience, etc. forbid contacting every individual.

Sample data: data from only some individual of interest
(are not complete and vary from sample to sample)
(N)
(n)

Draw conclusions about the whole (Population)!