Descriptive Statistics Measures of Skewness Kurtosis Descriptive Statistics

Descriptive Statistics Measures of Skewness & Kurtosis

Descriptive Statistics u Measures of Central Tendency • Mo • Mdn. • Mean u Measures • • of Variability Range Semi-Interquartile Range Average Deviation Standard Deviation u Measures of Skewness & Kurtosis

Skewness: Negative Skewness

Skewness: Positive Skewness

Descriptive Statistics u Measures based on Quartiles • Q 3 -Q 2< Q 2 -Q 1=Neg skewness • Q 3 -Q 2> Q 2 -Q 1=Pos Skewness • Pearsonian Measure of Skewness +1 Pos 0 Norm -1 Neg

Measures of Skewness u Measures based upon the third moment around the Mean. A Moment is a Deviation Score Raised to some POWER

Measures of Skewness u Measures based upon the third moment around the Mean. -1 Negative 0 Normal +1 Positive

Descriptive Statistics u Measures of Skewness • Pearsonian Measure of Skewness • Measures Based on 3 rd Quartile u Measures of Kurtosis • Kurtosis is a measure of the flatness or peakedness of a Distribution – Normal Kurtosis - Mesokurtic – Flat Kurtosis - Platokurtic – Peaked Kurtosis - Leptokurtic • A Measure of Kurtosis based on the 4 th moment about the Mean If less then 0 = Platokurtic More than 0 = Leptokurtic If 0 then = Mesokurtic

Descriptive Statistics 14 -Feb-97 The first test will cover material up to this point!!