More on Probability by David Palay
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Transcript of More on Probability by David Palay
More on Probability by David Palay
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Evaluate:
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In how many ways can the debate team choose a president and a secretary if there are 10 people on the team?
Mrs. Marshall has 11 boys and 14 girls in her class.A. How many ways can she select 2 girls to pass out a
snack?B. How many ways can she select 5 boys to pass out new
books?C. How many ways can she select 3 students to carry a
desk to the office?
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Definition of Experimental Probability:
Definition of Theoretical Probability:
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The Law of Large Numbers says, roughly, that as the number of trials increases,Experimental Probability approaches Theoretical Probability
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What is the probability that a point chosen randomly from within the rectangle will be within the shaded square?
4 in.
7 in.
2 in.
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2 3 4 5 6 7 8 9 10 11 120
5
10
15
20
25
30
4
8 7
14
2527
24
16
10 96
Rolls of 2 six sided dice
Sum
Tota
l occ
urre
nces
The above chart represents the outcome of 150 rolls of 2d6. What is the experimental probability of:
Rolling a 7?Rolling a 10 or higher? Rolling a 9 or Lower?
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Hmmm… Something interesting there about 10 and higher vs. 9 and lower…What do we get when we add them together?
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Interesting…What conclusion can we draw from this?
Compliments Rule
P ( A )+P ( Ac )=1
Combining events
P ( A∪B )=?
Venn Diagrams
Event A
New Symbols!Name Loose
TermsSymbol Example
Union Or
Intersection And
Compliment But Not
A∩B
A∪B
Ac
So how about these?
Addition rule for unions
The probability of A OR B is the Probability of A PLUS the Probability of B MINUS the Probability of A AND B
Mutual Exclusion
Two events are mutually exclusive if:• • There is no overlap• There is no possibility of them happening
together• No outcomes in
common
Change of Pattern
• In the following Venn Diagrams, we often assume that two events, A and B, constitute the entire Universe. That is, there is nothing outside of A and B.
Complimenting complex sets
What is the compliment of
What about ’s compliment?
So, algorithm
Write these on the Board…
The Monty Hall Problem
• Monty Hall, the host of Let’s Make a Deal, used to offer contestants this situation:– There are three doors, behind one is a great prize (Let’s go
with new car for the sake of our example) and behind the other two doors are fake prizes (goats, is the usual example here)
– The contestant is told to pick one door, but not to open it. The Host, Mr. Hall, then would open one of the two other doors to reveal one of the goats.
– The contestant is now given the opportunity to switch his/her choice to the as-yet untouched & unpicked third door.
Extra Practice
The chart describesthe transportation methods for 162travellers.
If a traveller is selected at random, what is the probability that:P(ferry or train)P(ferry or rental car)P(train and ferry, or train and rental car)