math 30 lecture 3 - PROBABILITY AND STATISTICS MEASURES OF...

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Unformatted text preview: PROBABILITY AND STATISTICS MEASURES OF VARIABILITY/ GROUPED DATA MATH 30: PROBABILITY AND STATISTICS Recall: • Mean is the average of all data values. • Median is the midpoint of all data values when arranged from lowest to highest. • Mode is the data value with the highest frequency. • Skewness refers to the symmetry (or the lack of symmetry) of the distribution. MATH 30: PROBABILITY AND STATISTICS MATH 30: PROBABILITY AND STATISTICS In summary, Measures of location Mean Median Mode Type of data I, R I, R, O N Extreme score problem Yes No No Always measurable Yes Yes No Number of values 1 1 0, 1, 2, … In/out of the set of data In/out In/out In Characteristics All scores are taken into account Middle value Popular value I – interval, R – rational, O – ordinal, N – nominal MATH 30: PROBABILITY AND STATISTICS Other Measures of Location Trimmed mean A trimmed mean is computed by “trimming away” a certain percent of both the largest and smallest set of values. For example the 10% trimmed mean is found by eliminating the largest 10% and smallest 10% and computing the average of the remaining values. MATH 30: PROBABILITY AND STATISTICS Other Measures of Location • QUANTILES are points taken at regular intervals from the cumulative distribution function of a random variable. • Dividing ordered data into q essentially equal- sized data subsets is the motivation for q- quantiles. MATH 30: PROBABILITY AND STATISTICS Other Measures of Location The popular quartiles are as follows: Quartile – One fourth m = 1,2,3 ?...
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This note was uploaded on 08/30/2011 for the course COMPUTER computer taught by Professor Ms during the Spring '10 term at Oxford University.

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math 30 lecture 3 - PROBABILITY AND STATISTICS MEASURES OF...

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