advanced algebra notes section 10.5: find probabilities of independent and dependent events
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Advanced Algebra NotesSection 10.5: Find Probabilities of Independent and Dependent Events
Two events are if the occurrence of one has no effect on the occurrence of the other. For instance, if a coin is tossed twice, the outcome of the first toss (heads or tails) has no effect on the outcome of the second toss.
independent
Probability of Independent Events If A and B are independent events, then the probability that both A and B occur is: More generally, the probability that n independent events occur is the product of the n probabilities of the individual events.
π ( π΄ππππ΅ )=π (π΄)βπ (π΅)
Example 1In a BMX meet, each heat consists of 8 competitors who are randomly assigned lanes from 1 to 8. What is the probability that a racer will draw lane 8 in the 3 heats in which the racer participates?
Example 2While you are riding to school, your portable CD player randomly plays 4 different songs from a CD with 16 songs on it. What is the probability that you will hear your favorite song on the CD at least once during the week (5 days)?
B is second heat C is third heat
π ( π΄ππππ΅ππππΆ )=π ( π΄)βπ (π΅ )βπ (πΆ)
ΒΏ18β18β18
ΒΏ115 β .00195
π (πππ‘ hπππππππ πππ )=
Hearing your song on Monday and Tuesday are independent
π (π»ππππππππππ )=1β[π (πππ‘ hππππππ hπ‘ ππ πππ )] 5
ΒΏ1β( )5
β0.763
Two events A and B are if the occurrence of one affects the occurrence of the other. The probability that B will occur given that A has occurred is called the of B given A is written as Probability of Dependent Events If A and B are dependent events, then the probability that both A and B occur is:
dependent events
conditional events
π ( π΄ππππ΅ )=π (π΄)βπ (π΅β¨π΄)
Example 4The table shows the numbers of tropical cyclones that formed during the hurricane seasons from 1988 to 2004. Use the table to estimate
a. The probability that a future tropical cyclone is a hurricane
b. The probability that a future tropical cyclone in the Northern Hemisphere is a hurricane.
π (π»π’πππππππ )=ΒΏππ π»π’ππππππππ πππ‘πππΆπ¦ππππππ
=β .483
ΒΏΒΏππ π»π’ππππππππ πππ . hπ»ππππ π ππππππ‘πππΆπ¦ππππππ πππ . hπ»ππππ π πππ
ΒΏ5451142β .477
Example 5You randomly select two cards from a standard deck of 52 cards. That is the probability that the first card is not a heart and the second is a heart if:a. You replace the first card before selecting the second b. You do not replace the first card?
π ( π΄ππππ΅ )=π ( π΄)βπ (π΅)ΒΏ3952β1352ΒΏ316β .188
π ( π΄ππππ΅ )=π ( π΄)βπ (π΅|π΄ )ΒΏ3952β1351
ΒΏ1368β .191
Example 6You and two friends go to the same store at different times to buy costumes for a costume party. There are 15 different costumes at the store, and the store has at least 3 duplicates of each costume. What is the probability that you each choose different costumes? A= Costume B= Different Costume Chosen C=Friend Choses a Third Costume
π ( π΄ ,π΅ππππΆ )=π ( π΄ )βπ (π΅|π΄ )βπ (πΆ|π΄ππππ΅ )
ΒΏ1515β1415
β1315
ΒΏ182225β .809