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Lecture

# Study

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School
Boston College
Department
Economics
Course
ECON 1151
Professor
Patrick Mc Gowan
Semester
Winter

Description
STATISTICS STUDY GUIDE Descriptive Statistics • Coefficient of Variation: CV= σ/μ   (The bigger the number, the more dispersion or variation) • Variance: ∑ (xi­μ)2/ n­1 (The sum of the squared differences between each observation and the sample  mean divided by the sample size, n, minus 1) • Skewness: negative, positive, symmetric Negative: (meanmedian) • Mean: ∑ xi/ n Where the summation of all x values divided by the number of x values Median: middle number Mode: number that occurs most often Range: highest­lowest value; IQR= Q3­Q1 • Five Number Summary Refers to the five descriptive measures: minimum, maximum, first quartile,  median, third quartile.  Q1: the value in the .25(n+1)th ordered position Q3: the value in the .75(n+1)th ordered position • Covariance: ∑ (Xi­μ)(Yi­μ)/ n­1 Where xi and yi are the observed values, μ is each respective mean, and n is the  sample size.    Poisson Approximation to the Binomial • The Poisson is always skewed right • If p20, you USE the Poisson to approx. • μ= np • example: P(x=0/μ=10) =0 Normal Approximation to the Binomial • n>20 • .05
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