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Unformatted text preview: 8-2 Statistics: Mean, Median, and ModeExample:We want to estimate the mean (average) beak-lengths of all yellow-cheeked warblers in Texas)Discussion:•if we could capture and measure every individual•we could obtain the population mean μ(“mu”)•instead, we will select a samplefrom the population•and compute the sample mean x(“x-bar”)Suppose we capture a sample of 10 and get measurements:2, 3, 3, 4, 5, 5, 5, 6, 6, 7 cm.Then x= (the average of these numbers) = 4.6 cm.•if we make n measurements: x1, x2, x3, … , xn•the sample mean is given by the formula:x= (x1+ x2+ x3+ … + xn)/nSummation (Σ= “sigma”) notation:•write x1+ x2+ x3+ … + xnas∑=niix1•read “the sum for i equals 1, 2, … up to n of the xi’s”•using this, the formula for the sample mean isx= nxnii∑=18-2p. 1Some more terminology:•we will frequently use the term scoreas the generic word for any kind of measurement or count•things like sample mean that are computed based on a sample, are called...
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This note was uploaded on 12/11/2011 for the course MATH 1324 taught by Professor Staff during the Spring '11 term at Austin Community College.
- Spring '11