Do you every watch a basketball game and think that a player has a “hot hand,” by making a lot of baskets consecutively? Do you ever play on slot machines and think that you are having a “streak” of good, or bad, luck? People often tend to see patterns in random events that are not really there.
But there’s a bit more to it than that. Are the odds of heads after flipping a coin always 50/50? Sure. That’s the basis for knowing that random assignment leads to equal probabilities of selection for each condition in an experiment. But what is the answer to the question: What are the odds of heads after flipping a coin when you have just obtained a head on the prior toss?
Read more about randomness at,
http://www.nytimes.com/2015/10/18/sunday-review/gamblers-scientists-and-the-mysterious-hot-hand.html
Does the logic of sampling on the basis of chance make sense to you as a way to achieve a representative sample?
Is it possible to do “better than chance” when choosing individuals in order to create two or more equivalent groups in an experiment?
Researching in a Social World 