In order to establish that the sample is truly random you need to obtain two main factors. First, is making sure that the random sample of both groups chosen (men and women) are equal in proportion to the overall population. Meaning both groups must be the same percentage of the overall population of the same gender. The second factor that you need to make sure of is that all chosen individual's had the exact same probability of being chosen from the population and no external factor influenced the probability of them being chosen for the study.
