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Unformatted text preview: Descriptive Statistics Regression Basics 06E:071:SCA Statistics for Strategy Problems Thomas Parker Fall 2011 T. Parker () Review 1 / 15 Descriptive Statistics Regression Basics Review : Outline Descriptive statistics The center of the data The spread of the data Associations between populations Regression basics Conditional Probability Regression estimate formulas T. Parker () Review 2 / 15 Descriptive Statistics Regression Basics The center of the data Suppose there is a population of things that have numerical values attached to them, and call them a population X = { X 1 ,... X N } . What are some ways we can describe the population? The mean probably needs no introduction, but just in case, = 1 N N i = 1 X i We will call the population mean . This is also known as the expected value of the population, and we write = E [ X ] , where the E reminds us that this is the value that you expect if you choose one value from X at random. Other ways of defining the middle of the data? T. Parker () Review 3 / 15 Descriptive Statistics Regression Basics Median and mode? When are they different from the mean? symmetric asymmetric T. Parker () Review 4 / 15 Descriptive Statistics Regression Basics Median and mode? When are they different from the mean? symmetric asymmetric mean median mode T. Parker () Review 5 / 15 Descriptive Statistics Regression Basics The spread of the data We will use the variance and the standard deviation. They are two ways of telling you the same thing: what is the dispersion of the observations? The variance Var ( X ) = 2 is defined by 2 = 1 N N i = 1 ( X i ) 2 The standard deviation is the square root of the variance. Why do we use the standard deviation? Given a sample, how do you calculate the variance by hand?...
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This note was uploaded on 09/26/2011 for the course 06E 071 taught by Professor Stuff during the Spring '11 term at University of Iowa.
 Spring '11
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