1)Mendel selected only pure breeding varieties of pea for his experiment.
2) he took only those traits for his studies which did not show linkage, interaction or incomplete dominance.
3) he took one or two characters at a time for his breeding experiments while his predecessors often studied all the traits simultaneously.
4) Mendel studied the inheritance of a character for 3 or more generations.
5) he performed reciprocal crosses and obtained large progenies. 6)Mendel experimented on a number of plants for the same trait and obtained hundreds of offspring. A large sampling n size gave credibility to his results.