A strength of Zimbardo's research (The Stanford Prison Experiment) is the rigourous methodology he used. The participants selected were all deemed to be mentally stable and the 24 participants were randomly allocated into one of two groups. This random allocation ensured that participant variables did not skew the results, for example the more submissive participants being put into the 'prisoner' group, and the more aggressive and sadistic participants being put into the 'guard' group. This is therefore a strength of Zimbardo's research as the sampling and allocation of participants was done in such a way to prevent extraneous variables affecting the results. However, ZImbardo's research has been criticized for overestimating the power of the situation. Zimbardo concluded that people conform to the social roles they are given/have. However, only 1/3 of guards acted sadistically and conformed to their social role. The other 2/3s of the guards either acted fairly or kindly. This therefore shows that people do not automatically adopted the behaviour that their social role dictates they should have, and ZImbardo therefore exagerated the extent to which people conform to social roles, and his mis-conclusion is a major weakness of the research.