Chance is an informal concept, sometimes meaning probability, sometimes meaning randomness. Probability is a formal mathematical concept expressed in its most simple form as dependent probability, which is a number between 0 and 1 that represents the likelihood that, for example, a person with one property will have another property. Thus the probability of a live birth being female is a dependent probability in which the two properties are “live birth” and “female.” Probabilities may also be assigned to beliefs. This kind of probability is known as subjective probability, and in this case the number represents the strength with which we think of a given belief to be true. Something is believed rather than known for certain because whether that thing is the case or not is merely probable. This is the kind of probability that one employs in making a bet with a friend about whether or not something is true.