q-q plot on Machine Learning

A q-q Plot or quantile-quantile plot graphs the quantiles of one univariate distribution against the corresponding quantiles of another. It is a powerful visualization tool in that it allows the user to view whether there is a shift in going from one distribution to another. 

Fig. shows a quantile-quantile plot for unit price data of items sold at two different branches during given time periods. Each point corresponds to the same quantiles for each data set and shows the unit price of items sold at branch 1 versus branch 2 for that quantile. To aid in comparison, we also show a straight line that represents the case of when, for each given quantile, the unit price at each branch is the same.

In addition, the darker points correspond to the data for Q1, the median, and Q3, respectively.

A Quantile-quantile plot for unit price data from two different branches