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##### Note 10: Measures of Central Tendency

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**Note 10: Measures of Central Tendency**• In statistics, there are 3 types of averages: • mean • median • mode Mode Median Mean - x The middle value when all values are placed in order The most common value (s) Affected by extreme values Not Affected by extreme values**Example:**Calculate the mean, median, and mode for this set of numbers 35 95 29 95 49 82 78 48 14 92 1 82 43 89 Arrange the numbers in order 1 14 29 35 43 48 49 78 82 82 89 92 95 95 median Mean – Median – halfway between 49 and 78, i.e. = 63.5 Mode – 82**Averages from a Frequency Table**Why is this mean misleading? Most students either do not buy their lunch at the canteen or buy it there every day. Calculate the mean = = = 2.3**The most common number of times people visit the canteen is**no times The median number of times students visit the canteen is the 17th data value. Adding the frequencies: 11 + 4 = 15 visited the canteen 1 time or fewer 11 + 4 + 3 = 18 visited the canteen 2 times or fewer Median must be 2 visits to the canteen.**For grouped data the midpoint of the interval, m, is used**instead of the exact x-values. f.m values are calculated and totaled.**Page 251**Exercise C and D