midterm2

# midterm2 - Coefficient of Variation (useful for comparing...

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Coefficient of Variation (useful for comparing the degree of dispersion in two or more distributions that have widely divergent means generally used only with data sets having a mean considerably larger than 0) cv = σ / μ cv = s / X Expressed as a percentage = (cv) x 100 Coefficient of Quartile Variation (less affected by extreme observations roughly a measure of how large the Quartile Deviation is relative to the median) CQV = (Q3 – Q1)/ (Q3+Q1) Expressed as a percentage = (CQV) x 100 Standard (z) Scores (The distribution of z Scores will have a mean equal to 0, std dev equal to 1) z=(x- μ)/ σ x = μ + (z)(σ) z’ = desired mean + (z)(desired std dev) Regardless of shape of the distribution, the shift to z scores always produces a distribution of standard scores with a mean of 0 and std dev of 1. Tchebycheff’s Inequality: Pr(|x- μ| >k σ) < 1/k 2 no more than (1/k 2 ) x 100% of the elements in a distribution are more than k std dev away from the mean. (k>1) Cantelli’s Inequality: Pr ( x - μ ≥ kσ ) 1/(1 + k 2 ) No more than (1/(1+k 2 )) x 100% of the elements in a distribution are above

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## This note was uploaded on 04/13/2008 for the course PSYC 60 taught by Professor Ard during the Winter '08 term at UCSD.

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midterm2 - Coefficient of Variation (useful for comparing...

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