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Unformatted text preview: STA 100 Lecture 3 Paul Baines Department of Statistics University of California, Davis January 7th, 2011 Admin for the Day I Homework 1 posted, due Wednesday, Jan 12th in class I Electronic submissions are not valid: We must receive a paper copy I Handwritten or printed versions are both fine I If you complete your homework on computer (e.g., doc, pdf) then please also submit it to Smartsite via the Assignments tab I Smartsite submission not required if you handwrite your homework solutions I Detailed R and R Commander Instructions Online Admin for the Day I Homework 1 posted, due Wednesday, Jan 12th in class I Electronic submissions are not valid: We must receive a paper copy I Handwritten or printed versions are both fine I If you complete your homework on computer (e.g., doc, pdf) then please also submit it to Smartsite via the Assignments tab I Smartsite submission not required if you handwrite your homework solutions I Detailed R and R Commander Instructions Online References for Today: Rosner, Ch 2.12.12 (7th Ed.) Topics For Today 1. Exploratory Data Analysis: 2. Descriptive Statistics: Exploratory Summaries We have seen some graphs – lets look at other descriptive statistics. Measures of Center Mean The ‘average’ value: Median The middle value. Mode The most common value. Measures of Center Mean The ‘average’ value: ¯ x = 1 n n X i =1 x i (1) Median The middle value. Mode The most common value. Measures of Center Mean The ‘average’ value: ¯ x = 1 n n X i =1 x i (1) Median The middle value. Median ( x ) = x ( n +1 2 ) if n is odd 1 2 x ( n 2 ) + x ( n 2 +1 ) if n is even (2) where x ( i ) denotes the i th smallest value i.e., x (1) = min , x ( n ) = max . Mode The most common value. Beyond the Center The median naturally describes the center of a distribution. What other quantities might we want to describe? Beyond the Center The median naturally describes the center of a distribution. What other quantities might we want to describe? Definition Percentiles Definition 2.6, Rosner: Define the p th percentile by: 1. The ( k + 1)th largest value, if np / 100 is not an integer (where k is the largest integer less than np / 100 ). 2. The average of the np / 100th and ( np / 100 + 1)th largest values, if np / 100 is an integer. Beyond the Center The median naturally describes the center of a distribution. What other quantities might we want to describe? Definition Percentiles Definition 2.6, Rosner: Define the p th percentile by: 1. The ( k + 1)th largest value, if np / 100 is not an integer (where k is the largest integer less than np / 100 ). 2. The average of the np / 100th and ( np / 100 + 1)th largest values, if np / 100 is an integer....
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 Spring '10
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 Statistics, Quartile, San Diego

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