Here's a quick and easy way to randomize. you hove 100 subjects, 50 women and 50 men. toss a coin. if it's heads, assign the men to the treatment group and the women to the control group. if the coin comes up tails, assign the women to treatment and the men to control. this gives every individual subject a 50-50 chance of being assigned to treatment or control. why isn't this a good way to randomly assign subjects to treatment groups?
a. the result of a coin toss is not really random.
b. the probability of a coin to fall on each side is not the same.
c. we can't be sure that the composition of two groups will be similar.
d. the coin might be lost.