# proportion between test and train set in regression and classification

Many claim different proportion between test and train set in regression and classification telling this should be test:train : 0.25:0.75 or 0:33:0:66 (the most popular with what I met). But what with proportions 0.1:0.9 or even 0.05:0.95? I am asking because there are over 1,2 mln observations in a set I'd like to analyze and 0.05 from 1,2 mln is a huge number itself (60000).

Classification requires a much larger sample size than prediction if classification involves categorizing $Y$ so beware.