Milgram's research lacked population validity. Milgram used a bias sample of 40 male volunteers, which means we are unable to generalise the results to other populations, in particular females, and cannot conclude if female participants would respond in a similar way. This study was conducted in the US which is an individualistic culture meaning it will be hard to generalise to collectivist cultures like in china This means Milgram's findings tell us little about obedience in women and people from some cultures.