https://stat.ethz.ch/R-manual/R-devel/library/stats/html/chisq.test.html

Source:
svn+ssh://stamarit@kaz.dsic.upv.es/concurrency/ITICSE%202013/figures/excels/Cuando%20se%20sientan%20los%20que%20se%20dejan%20la%20asignatura.xlsx