Knowledge of statistics, ever since its inception, has served every aspect of human life and every individual and social class. It has shown its extraordinary potential in dealing with numerous problems encountering human beings since the occurring of Covid-19 in Wuhan, China. A vast amount of literature has appeared showing the power of the science of statistics in answering different questions regarding this disease and all its consequences. But it comes short of, as an instance, in modelling the geometry of disease spread among societies and in the world as a whole. Here the only way to deal with this matter is to resort to probability theory and its many ramifications in providing realistic models in describing this spread. A very power tool in this regard is percolation theory, which besides its many applications in mathematical physics, is very handy in modelling epidemic diseases, among them the Covid-19.  A short description of this theory with its use in modelling the spread of epidemic deceases, shows the importance of dealing with probability as a separate subject in the curricula and not a subordinate of the science of statistics which is now dominant in the statistics major curricula in the Iranian schools.