What is mean?
Mean is the average of numbers.
Example:
3, 5, 6, 9, 8
Mean = all values/Total number of values
Mean = 3+5+6+9+8/5
Mean = 6.2
How to calculate the mean for data with frequencies?
Age  Frequency  Age * Frequency 
22  5  22 * 5 = 110 
33  2  33 * 2 = 66 
44  6  44 * 6 = 264 
66  4  66 * 4 = 264 
Total  17  704 
Mean = 704/ 17
Mean = 41
What is Median?
Median is the middle value among all values.
How to calculate the median for an odd number of values?
Example:
9, 8, 5, 6, 3
Arrange values in order
3, 5, 6, 8, 9
Median = 6
How to calculate median for an even number of values?
Example:
9, 8, 5, 6, 3, 4
Arrange values in order
3, 4, 5, 6, 8, 9
Add 2 middle values and calculate their mean.
Median = 5+6/2
Median = 5.5
What is Mode?
The mode is the most occurring value.
How to calculate mode?
Example:
3, 6, 6, 8, 9
Mode = 6 (because 6 is occurring 2 times and all other values occur only one time).
Why mean median and mode are equal in normal distribution?
The normal distribution is not dealing with skewed distributions. The mean, median, and mode are equal in normal distribution.
For example, if we have a sample data, then Half of the population is greater and half is less than mean.
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