Variance: spread of data
standard deviation
17, 19, 18, 17, 19 -> mean=18
-1 1 0 -1 1
variance = 0.8
std deviation = 0.8944
7, 38, 4, 23, 17 -> mean=18
-11 20 -14 5 0
variance = 148.4
std deviation = 12.18
mean = μ
variance
1/n Σ(Xi – μ)^2
standard deviation = √variance
data 3,4,5,6,7
mean 5
variance 2
std dev 1.414
data 8, 9, 10, 11, 12
mean 5
variance 2
std dev 1.414
data 15, 20, 25, 30, 35
mean 25
variance 50
std dev 7.071
