Measures of variability

Exploratory Data Analysis in R

Andrew Bray

Assistant Professor, Reed College

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x - mean(x)

 1.4545  3.4545  0.4545 -0.5455  1.4545 -2.5455
-0.5455 -1.5455 -1.5455  0.4545 -0.5455

sum(x - mean(x))

-1.421085e-14

sum((x - mean(x))^2)

28.72727

n <- 11
sum((x - mean(x))^2)/n

2.61157

sum((x - mean(x))^2)/(n - 1)

2.872727

var(x)

2.872727

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sd(x) # Standard deviation

1.694912

var(x) # Variance

2.872727

summary(x)

 Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
72.00   73.50   74.00   74.55   75.50   78.00

IQR(x) # Interquartile range

diff(range(x)) # Range

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x_new

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sd(x_new) # Was 1.69

6.987001

var(x_new) # Was 2.87

48.81818

diff(range(x_new)) # Was 6

IQR(x_new) # Doesn't change

Let's practice!

Exploratory Data Analysis in R