Page 9 - Statistics presented by Dr. Sara Ismail Aborass

9/8/2023

Measures of Central Tendency–Arithmetic Mean

 The most widely used measure of central value is the mean, ഥ .
The mean, also called the arithmetic mean or the average, is
obtained by dividing the sum of replicate measurements by the

number of measurements in the set:

N.B: change the capital N for sample n
number of data or results to be small
(n) to differentiate it from the N
(number of population data)

To emphasize the difference between the two means, the sample mean
is symbolized by ഥ and the population mean by μ.

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Measures of Central Tendency–Median

◉ The median is the middle result when replicate data are
arranged in increasing or decreasing order. There are
equal numbers of results that are larger and smaller than
the median.

◉ For an odd number of results, the median can be found
by arranging the results in order and locating the middle
result. For an even number, the average value of the
middle pair is used as shown in Example.

◉ The median is robust, i.e. it is not affected by extreme
values or outliers (Lab).

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