Measures of Variation

Question 1

Range

Answer 1

Range = Highest value - lowest value

Question 2

Standard deviation

Answer 2

Measure of the amount of variation of a random variable expected about its mean

Low SD, values tend to be closer to mean
High SD, values are spread out over a wider range

Ungrouped data
Grouped data - f is multiplied to (x-x̄)^2

Question 3

Population standard deviation (σ)

Answer 3

σ = sqr[(summ(x - x̄)^2)/(N)]

Question 4

Sample standard deviation (S)

Answer 4

S = sqr[(summ(x - x̄)^2)/(n-1)]

n-1 - correction factor

Question 5

Variance

Answer 5

Square of the standard deviation