3  Variability

• Range

\[ Range = \text{max}(x) - \text{min}(x) \]

• Variance

\[ Variance = \sigma^2 = \frac{1}{N}\sum_{i=1}^{N}(x_i-\bar{x})^2 \]

• Standard Deviation

\[ Standard Deviation = \sigma = \sqrt{\text{Variance}} \]

ct <- c(1,1,1,1,1,1,1,1,2,2,2,2,2,2,3,3,3,3,3,4,5,5,6,6,14)
mean_ct <- mean(ct)

vr <- sum((ct-mean_ct)^2)/(length(ct)-1)
sd <- sqrt(vr)