Statistics

Recall the following terms.
Mean = all data sum up/ number of terms
Median = the data separating the upper half and lower half

Case 1 (Odd number of terms) : 1,2,3,4,5
5/2 = 2.5 which is not an integer. So, another way to go.
Left-hand side of 3 : 1,2 (2 terms)
Right-hand side of 3 : 4,5 (2 terms)
Thus, median is 3

Case 2 (Even number of terms) : 1,2,3,4,5,6
6/2 = 3
Thus, the upper half and lower half should each involve 3 terms.
Thus, median = (3rd term + 4th term) / 2 = (3 + 4) / 2 = 3.5

Range = largest term - smallest term
Lower quartile = median of the lower half
Upper quartile = median of the upper half
Inter-quartile = upper quartile - lower quartile
Standard deviation increases when data become dispersed. 
(E.g. mean data is removed)
Standard deviation decreases when data become concentrated.
(E.g. mean data is added)
Variance = (Standard deviation)2

	Each data plus x	Each data times x
Mean	Plus x	Times x
Median	Plus x	Times x
Range	Unchanged	Times x
Upper quartile	Plus x	Times x
Lower quartile	Plus x	Times x
Inter-quartile	Unchanged	Times x
Standard deviation	Unchanged	Times x
Variance	Unchanged	Times x2