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lecture2

# lecture2 - Crashing decisions have been made Labs this week...

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Crashing decisions have been made Labs this week! Website gauchospace.ucsb.edu Bedrock principles that have nothing to do with math Populations and samples Types of research Types of variables What are statistics? Set of tools, vocabulary, and symbols for communicating about data Permits one to: organize, summarize, present, and interpret information Theory about decision making How to make judgments when one is uncertain

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There are two main branches of statistics Descriptive Statistics Tools for summarizing data Tables & graphs measures of central tendency measures of variability Inferential Statistics Data from a sample is used to draw inferences about a population Tools for generalizing beyond actual observations (from a sample to a population) Population The set of all individuals of interest Does not have to be humans (could be tires, bears, bugs) Doesn t have to be a big group Sample A set of individuals selected from a population Usually intended to represent the population There are two main sources of data Political polls Population: All voters Sample: The individuals polled US University Undergraduates Population: Students at US universities Sample: UCSB undergraduates
We need to know how to tell the difference between when we are talking about populations and samples Parameter Any characteristic coming from a population (e.g., the average) Usually denoted by a Greek character Statistic Any characteristic coming from a sample Usually denoted by an English character Although we typically deal with information coming from a sample, we usually want to know something about a population Because populations are usually too big to completely characterize we have to rely on samples This is tricky business because of Sampling error

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