Transcript Probability

We cannot predict the future.
When we make decisions, we instinctively
use probability theory.
3 of your friends go to
Frizzie’s Beauty Parlor
2 of them emerge BALD!
FRIZZIE’S
Beauty Parlor
You decide that you will never go to Frizzie’s
4 of your friends buy cars at FBN (Fly By Night) Autos
2 of them are lemons
FBN
AUTOS
You decide that you will never buy a car from FBN
3 of your friends ski
Mount Killerdare
2 of them break legs
You decide that you
will never ski Mount
Killerdare.
CONSIDER THE FOLLOWING GAME:
A box contains
3 black and 5 white marbles.
Draw one marble from the box. You win if it is black.
A box contains
3 black and 5 white marbles.
Draw one marble from the box. You win if it is black.
There are 3 chances
out of 8
of winning this game.
We say that the probability of winning = 3/8 = .375 = 37.5%
Note: there are two numbers involved in this measurement the number of ways to win (# favorable outcomes) and the
total number of marbles (# possible outcomes)
A box contains
3 black and 5 white marbles.
When the game is to draw just one marble from the box, we can
intuitively measure the probability of getting a black marble.
Now change the game slightly. Draw two marbles at once from
the box. You win if both are black.
When counting the favorable outcomes you must consider ….
When counting the possible outcomes you must consider ….
There are 28 pairs of marbles in this box!
We must develop techniques
for counting!