13_Ch12_Estimation

# 13_Ch12_Estimation - 11/24/10 Overview Estimation...

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11/24/10 1 Psychological Statistics - Estimation - PSY 207 Overview • Estimation – Point estimation – Interval estimation – Confidence intervals • Constructing confidence intervals • Sample size and confidence intervals • Confidence vs. Precision Estimation We have previously discussed testing hypotheses about a population We may also be interested in estimating a population mean. .. – ... to determine the size of an effect – ... to determine information about a population We can use sample characteristics and test statistics to estimate population means Estimation Estimation is the process of using sample statistics to estimate population parameters. The objective of estimation is to determine the approximate value of a population parameter on the basis of a sample statistic.

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11/24/10 2 Estimation Known sample with M and SS Unknown population Estimation Sampling Error Two types of estimates Point estimates Interval estimates Point estimates For a point estimate , you use a single number as your estimate of an unknown quantity. Very precise : a single, exact number But no information about confidence . The point estimate for the population mean (μ) is the sample mean (M). Interval estimates For an interval estimate , you use a range of values as your estimate of an unknown quantity. When an interval estimate is accompanied by a specific level of confidence (probability), it is called a confidence interval . We say (with some % certainty) that the population parameter of interest is between some lower and upper bounds.
11/24/10 3 What is the average amount of money that customers spend on Black Friday ? Friday Point estimate: \$350 Interval estimate: \$250-\$450 Confidence Intervals • Interval estimate accompanied with a specific level of confidence. • Range of values within which we are reasonably confident the population mean lies. • In fact, we can specify exactly how confident we are.

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## This note was uploaded on 08/22/2011 for the course PSY 207 taught by Professor Pfordesher during the Fall '07 term at SUNY Buffalo.

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13_Ch12_Estimation - 11/24/10 Overview Estimation...

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