2.4 Determine Probability (Part 1)

Key ConceptThe probability of a chance event uses a number between 0 and 1 to describe the likeliness that the event will occur. You can use the number of total and favorable outcomes of an event, to determine the probability of simple or compound events.Lesson Objectives- Determine the Probability of Simple Events- Determine the Probability of Compound EventsCore Skills Practices- Determine Probabilities Probability of Simple Events Genetic traits, like eye color, are inherited from your parents; theirs from their parents, and so on. You can analyze possible combinations in order to find the probability that your children will have certain colored eyes or other genetic traits. For this spinner, write the probability of spinning blue as the ratio of the number of blue sections in the spinner (favorable outcomes) to the total number of sections in the spinner (total outcomes). The probability of spinning blue is 3 out of 4. Probability FactsHere are some other important facts to know about probabilities expressed as numbers.- If there is no chance that an event can happen, the probability is 0.- If an event is certain to happen, its probability is 1, or 100%.- The greater the probability that an event will occur, the closer the number will be to 1 or 100%; the less likely the probability, the closer the number will be to 0.- The sum of the probability of an event and its complement is 1.- If two events are equally likely, the probability of each is 50%. Find Favorable OutcomesFor many probability problems, making a list of possible outcomes is the best first step. Use your list to count total outcomes and favorable outcomes. Tree DiagramsAnother way to count outcomes is to draw a tree diagram, which resembles a branching tree. Each identifies a possible outcome of an experiment. You can also base probability on past performance or on data. This type of probability is called experimental probability. Think About MathAnswer the following questions. If you flip a pair of coins 48 times, how many times are you most likely to get 2 heads? 10 12 14 184 I'm still flipping coins... A basketball player makes 15 free throws out of his last 45 attempts. How many free throws is he most likely to make out of his next 90 attempts? 90 60 45 30 15