Probability
Introduction
Probability
Events
Outcome is an event. Events can be:
- impossible, probable and certain
- dependent or independent
Events
Impossible event: The one that can’t happen.
- out of all Y7 students, pick one who is a door
Probable: The one that might happen.
- out of all Y7 students, pick a female student
Certain: The one that will happen
- out of all Y7 students, pick a living being
Events
Dependent event – relies on another event to happen first
-
Robbing a bank and going to jail.
-
Not paying your power bill on time and having your power cut off.
-
Boarding a plane first and finding a good seat.
-
Parking illegally and getting a parking ticket. Parking illegally
increases your odds of getting a ticket.
-
Buying ten lottery tickets and winning the lottery. The more tickets
you buy, the greater your odds of winning.
-
Driving a car and getting in a traffic accident.
Events
Independent event – the event has no effect on a probability of
another event happening
•
Owning a dog and growing your own herb garden.
•
Paying off your mortgage early and owning a Chevy Cavalier.
•
Winning the lottery and running out of milk.
•
Taking a cab home and finding your favorite movie on cable.
Example 1: If we roll a dice, find a
probability of:
A = „We got 1.”
1
𝑝 𝐴 =
6
B = „We got an even number.”
-that means we got either 2, 4 or 6 so: 𝑝 𝐵 =
C = „We got 7.”
0
𝑝 𝐶 = =0
6
1+1+1
6
3
1
=6=2
Example 2:
Playing deck of cards has:
52 cards
4 suits (spades, clubs, hearts, diamonds) – 13 of each kind
2 colours (black and red)
Numbers 2-10, ace, jack, queen, king
Example 2:
Example 3: Find a probability of:
A=„We picked a red card.”
26 1
𝑝 𝐴 =
=
52 2
B=„We picked a diamond.”
13 1
𝑝 𝐵 =
=
52 4
C=„We picked a red 10.”
2
1
𝑝 𝐶 =
=
52 26
Task 1: You have a black bag with 50 candy. 14
have strawberry flavour, 23 are menthols nad the
rest of them are chocolate. Find a probability of:
a) A=„Picking a chocolade one.”
b) B=„Picking a sweet one.”
c) C=„Picking a candy.”
d) D=„Picking a hammer.”
Tasks
Tasks
Tasks