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Measures of Central Tendency for Ungrouped Data. Section 3.1. Mean. Mean = Sum of all Values Number of Values Mean from a sample is x = ∑x/n Mean from population is µ = ∑x/N Mean is very sensitive to outliers. Identity Fraud Victims in 2004 for Six States.
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Measures of Central Tendency for Ungrouped Data Section 3.1
Mean • Mean = Sum of all Values Number of Values • Mean from a sample is x = ∑x/n • Mean from population is µ = ∑x/N • Mean is very sensitive to outliers.
Median • Middle term of data after ranked in increasing order. • Divides data into two equal parts. • Not influenced by oultiers.
Mode • Value with the highest frequency in a data set. • Not all data sets have a mode. • Some data sets have more than one mode. • Unimodal – One mode. • Bimodal – Two modes. • Multimodal – More than two modes.
Comparisons of Measures of Center • Mean is most common and each member of the data set is used in its calculation. • Median is better if the data set contains outliers. • Mode is the easiest to locate, but not much use.
Mean, median, and mode for a symmetric histogram and frequency distribution curve.
Mean, median, and mode for a histogram and frequency distribution curve skewed to the right.
Mean, median, and mode for a histogram and frequency distribution curve skewed to the left.