Chapter 21 - Chapter 21 Notes (Students) What Is A...

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Chapter 21 Notes (Students) 1 What Is A Confidence Interval? • Statistics is the science of collecting, classifying, presenting, and interpreting data. • Two Areas of Statistics – Descriptive Statistics : Methods of summarizing or describing a set of data – Inferential Statistics : Methods of making generalizations about a population based on a sample. • Two Inferential Techniques – Estimation (Confidence Intervals) – Hypothesis Testing Parameters and Statistics • Parameter – a number that describes a population; it’s a fixed number, but we usually do not know its value. • Statistic – a number that describes a sample; its value is computed from sample data and 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
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2 Estimation • Goal is to estimate the value of an unknown population parameter. • Determining the Parameter Mean; Average μ Proportion; Percentage p Key Words Statistic Parameter p ˆ x Interval Estimates • Even the most efficient unbiased estimator is unlikely to estimate the population parameter exactly. • In many situations, it is preferable to determine an interval within which we would expect to find the value of the parameter. • A confidence interval (interval estimate) is a formula that tells us how to use sample data to calculate an interval that estimates a population parameter. Proportions • We want to estimate the proportion of individuals in a population with a certain characteristic (“success”). • The population proportion, p, is an unknown parameter. • We wish to estimate p based on a sample. • Take a SRS of size n from a population with p successes. is the sample proportion where
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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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Chapter 21 - Chapter 21 Notes (Students) What Is A...

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