Probability Basics
The chance of flipping heads on a fair coin.
1/2
A diagram made of circles showing how groups overlap.
a Venn diagram
This tool helps us calculate probability when groups share people or items.
a Venn diagram
The total number of possible outcomes.
the sample space
1,729,397.01234213 X 0
0
The chance of rolling a 6 on a regular dice.
1/6
In a Venn diagram, this section shows people who are in both groups.
the intersection
You pull a name from a Venn diagram. It lands in both circles. What’s the probability
the number in the overlap divided by the total
What does “mutually exclusive” mean
events that cannot happen at the same time
If x = 5, what is the value of 3x + 2?
17
A bag has 5 blue and 5 red counters. What's the chance of picking a blue one?
1/2
How many parts are in a 2-circle Venn diagram?
4 (Group A only, Group B only, Both, Neither)
There are 20 students. 12 like maths, 9 like English, 5 like both. What’s the probability a student likes neither
20 – (12 + 9 – 5) = 4, so 4/20 or 1/5
What does the symbol ∪ mean
union (A or B)
How many degrees are in a right angle
90°
A result that will never happen has this probability.
0
If someone is not in either group, where do they go in the diagram?
outside the circles
From a Venn diagram, 6 students like dogs, 4 like cats, 2 like both. What’s the total number of students
6 + 4 – 2 = 8
What does the symbol ∩ mean
intersection (A and B)
What is 10% of $100,000
$10,000
The probability of something certain to happen.
1
You place a person in only one circle. What does that mean
they belong to one group only (not both)
You’re told P(A) = 0.3, P(B) = 0.4, and P(A ∩ B) = 0.1. P(A ∪ B)
0.3 + 0.4 – 0.1 = 0.6
Explain the difference between theoretical and experimental probability.
: theoretical is based on maths, experimental is based on real trials
Solve X
3x+5=20
x = 5