Exam 2 Cheat Sheet

# Exam 2 Cheat Sheet - Statistics Summer 2007 Exam 2 Cheat...

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Statistics Summer 2007 Exam 2 Cheat Sheet Observational Study - Observes individuals and measures variables of interest but does not attempt to influence the responses; describes some group or situation. Experiment - Deliberately imposes some treatment on individuals in order to observe their responses; purpose of an experiment is to study whether treatment causes a change in response. Confounded - Two variables are confounded when their effects on a response variable cannot be distinguished from each other. Population - Entire group of individuals about which we want info. Sample - A part of a population from which we actually collect info; we use a sample to draw conclusions about entire populations. Sample Design - Describes exactly how to choose a sample from the population. Biased - If a design of a statistical study systematically favors certain outcomes. Voluntary Response Sample - People who choose themselves by responding to a broad appeal. They are biased. Simple Random Sample (SRS) - Of size n consists in such a way, every set has an equal chance to be selected. Table of Random Digits - A long stride of the digits 0, 1, 2, …, 7, 8, 9 o Each entry is equally likely to be any of the 10 digits 0-9. o The entries are independent of each other. Using Table B : o Step 1 : Label : give each member of the population a numerical label of the same length. o Step 2 : Table : Read from Table B successive groups of digits of the length you used as labels. Probability Sample - Sample chosen by chance. Stratified Random Sample - First classify the population into groups of similar individuals called Strata . Then choose a separate SRS in each stratum and combine these SRSs to form the full sample. Undercoverage

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Exam 2 Cheat Sheet - Statistics Summer 2007 Exam 2 Cheat...

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