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Mean, Median and Mode

Mean:
A simple or arithmetic average of a range of values or quantities, computed by dividing the total of all values by the number of values. For example, the mean of 1, 2, 3, 4, and 5 is (15 ÷ 5) = 3. It is the most common and best general purpose measure of the mid-point (around which all other values cluster) of a set of values, but is prone to distortion by the presence of extreme values and may require the use of a measure of distortion (such as mean deviation or standard deviation). Also called arithmetic mean.
Example 1: What is the Mean of these numbers?
6, 11, 7
·         Add the numbers: 6 + 11 + 7 = 24
·         Divide by how many numbers (there are 3 numbers): 24 / 3 = 8
Median:
Value or quantity that falls halfway between a set of values arranged in an ascending or descending order. When the set contains an odd number of values, the median value is exactly in middle. If the number of values is even, the median is computed by averaging the two numbers closest to the middle.
Example:
3, 13, 7, 5, 21, 23, 23, 40, 23, 14, 12, 56, 23, 29
When we put those numbers in order we have:
3, 5, 7, 12, 13, 14, 21, 23, 23, 23, 23, 29, 40, 56
There are now fourteen numbers and so we don’t have just one middle number, we have a pair of middle numbers:
3, 5, 7, 12, 13, 14, 21, 23, 23, 23, 23, 29, 40, 56
In this example, the middle numbers are 21 and 23.
To find the value halfway between them, add them together and divide by 2:
21 + 23 = 44
then 44 ÷ 2 = 22
MEASURES OF DISPERSION:
Dispersion in statistics is a way of describing how to spread out a set of data is. When a data set has a large value, the values in the set are widely scattered; when it is small the items in the set are tightly clustered. Very basically, this set of data has a small value:
1, 2, 2, 3, 3, 4
…and this set has a wider one:
0, 1, 20, 30, 40, 100
The spread of a data set can be described by a range of descriptive statistics including variance, standard deviation, and interquartile range. Spread can also be shown in graphs: dot plots, boxplots, and stem and leaf plots have a greater distance with samples that have a larger dispersion and vice versa.
Image result for scatter plot in measure of dispersion 

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