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EX ST 222 Exam 1 Study Guide

# EX ST 222 Exam 1 Study Guide - EX ST 222 Exam 1 Study Guide...

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EX ST 222 Exam 1 Study Guide Statistics in Everyday Life: Units o Individuals o Objects (people, animals, things) described by a set of data Variable o Characteristic of units that can take different values for different units Example: o Poll students Student is the unit Variable could be sex, major, age, GPR, height, opinion Population o Set of all measurements of interest for a particular group o When expressing a population you must express the variable and the population of units Sample o The subset of measurements from population of interest o Samples must be random and representative Example: o Ask registered voters if they agree with a certain issue The population would be the opinions of all registered voters The sample would be the opinions of selected registered voters Parameter o A number calculated from a population o The parameter is the true value Ex: µ is the population mean Ex: p is the population proportion Statistic o A number calculated from a sample o A statistic is an estimation of a parameter and is also called the point estimate X bar is the sample mean S 2 is the sample variation S is the sample standard deviation P^ is the sample proportion P and P Hat o Are used for qualitative P is the true proportion P hat is the sample proportion X Bar and µ o Used for quantitative

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o µ is the true average o X Bar is the sample average Observational studies o Observe individuals and measure variables of interest o No attempt is made to influence the responses o Observer looks for patterns o Purpose: describe some group or situation Sample surveys o Type of study in which a selected group is surveyed because they represent the entire group o Type of observational study o Ex: public opinion polls Census o Type of study that attempts to include the entire population o Don’t need statistics Experiments o In observational studies just want to observe but not disrupt natural behavior o In experiments impose treatments and observe responses o The purpose of the experiment is to study whether the treatment has an effect on the response o Must have clearly defined goals before conducting the experiment Statistics in Society: Everyone has an agenda, a motive
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EX ST 222 Exam 1 Study Guide - EX ST 222 Exam 1 Study Guide...

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