Original Source Material

Student Version

Psychologists have found that people tend to forget that a head is just as likely to be followed by a head as by a tail; therefore they have too many reversals, and too few strings of heads, in their successive guesses. If a fair coin toss comes up heads thirty times in a row, the next toss is still equally likely to be heads or tails.

References:
Dixit, A. K., & Nalebuff, B. J. (1991). Thinking strategically: The competitive edge in business, politics, and everyday life. New York, NY: Norton.

Consider an individual trying to produce a random series of heads or tails decisions without any external aid. People aren't good at being random; “therefore they have too many reversals, and too few strings of heads, in their successive guesses” (Dixit & Nalebuff, 1991, p. 184). This example helps to illustrate the difficulty of producing truly random data.