STAT1051_lesson4-1

STAT1051_lesson4-1 - Descriptive Statistics Numerical...

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Descriptive Statistics Numerical Summary
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2 Summation Notation Observations in a dataset are denoted by { x 1 ,x 2 ,x 3 ,x 4 ,.... x n }; n = sample size x 1 is the first observation, x 2 is 2nd obs. and so on. We use ∑ x i to denote x 1 + x 2 + x 3 + x 4 +.…+ x n In particular, n n i i x x x x + + + = = ...... 2 1 1
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3 Example 5.0 Suppose a dataset contains obs . {3.5,11.2,8,.4,5.4}, Then n=5 , and 28.5 5.4 .4 8 11.2 3.5 = + + + + = + + + + = = 5 4 3 2 1 5 1 x x x x x x i i 231.01 5.4 .4 8 11.2 3.5 2 2 2 2 2 = + + + + = + + + = = 2 5 2 2 2 1 5 1 2 .. x x x x i i 812.25 28.5) 2 2 = = = ( ) ( 5 1 i i x Not Same
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4 Population and Sample POPULATION Collection of all the units that we are interested in studying. SAMPLE A subset of the units of the population.
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5 Numerical Summary Want to summarize the data using numerical descriptive measures. Two quantities to measure: I. CENTER Measure of central tendency II. VARIABILITY Spread of the data Both population and sample data can be summarized.
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6 Central Tendency We want to locate the center of the data in three ways MEAN MEDIAN MODE
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This note was uploaded on 11/27/2011 for the course STAT 1051-10 taught by Professor Balaji during the Fall '11 term at GWU.

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STAT1051_lesson4-1 - Descriptive Statistics Numerical...

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