Chapters 3 and 4

Chapters 3 and 4 - Chapters 3 and 4 Notes (Student) What Do...

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Chapters 3 and 4 Notes (Student) 1 What Do Samples Tell Us? • Does the number describe a sample or a population? • Parameter – a number that describes the population. It’s a fixed number, but we usually don’t know its value. • Statistic – a number that describes a sample. Its value is computed from sample information, but it can change from sample to sample. The Big Picture Population Sample Statistic Parameter select estimate calculate describes True proportion True mean Sample proportion Sample mean Error in Estimation • We wish to estimate a parameter from a statistic. •B i a s – consistent, repeated deviation of the sample statistic from the population parameter in the same direction when we take many samples. • Variability – describes how spread out the values of
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Chapters 3 and 4 Notes (Student) 2 Managing Bias and Variability • To reduce bias, use random sampling. Produces unbiased estimates of the parameter. • To reduce the variability of a SRS, use a larger sample. Bias and Variability Margin of Error • A statistic, calculated from a random sample, will usually not estimate the parameter exactly. • Surveys often report a percentage and a “margin of
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This note was uploaded on 02/14/2011 for the course STAT 110 taught by Professor Johnson during the Fall '07 term at South Carolina.

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Chapters 3 and 4 - Chapters 3 and 4 Notes (Student) What Do...

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