QQ Plot

• Quantile to Quantile Plot

• Quantile:– Points taken at regular intervals from the

cumulative distribution function (CDF) of a random variable

• QQ Plot:– Graphical method for comparing two

probability distributions by plotting quantiles of their values against each other

– Does not include spatial-temporal information

Wikipedia

Quantiles

• If the data set have 10 values of:– 3, 6, 7, 8, 8, 10, 13, 15, 16, 20

• 4 quantiles would result in:– 10 x ¼ = 2.5, rounded to 3 => 7– 10 x ½ = 5 => 8– 10 x ¾ = 7.5, rounded to 8 => 15

Normal QQ Plot

Normal QQ Plot?

Resampling

• Bootstrapping – Drawing sets of samples, with replacement

from the original dataset– Different results each time

• Jackknifing– Repeat the estimation leaving out part of the

dataset each time– Repeatable

• Work with any interpolation or trend-surface method