Probability - Topic 3

Question 1

Year 1 - Chapter 6.1

What is it called when all of the probabilities are the same?

Answer 1

Discrete uniform distribution

Question 2

Year 2 - Chapter 2.1+2

All types of set notation:

Answer 2

• P(A∩B) - A intersection B (A and B), the area of the diagram where both A and B overlap
• P(A∪B) - A union B (A or B), the area of the diagram where data is in either A or B
• P(A’) - not A, the area of the diagram that isn’t in A; 1 - P(A) = P(A’)
• P(A’∪B’) - Means the same as P(A∩B)’; everything apart the intersection of A∩B
• P(A|B) - The probability of A given B has already occurred
• P(A|B’) - The probabilty of A given B has not happened

Question 3

Year 2 - Chapter 2.4

All types of probability formulae:

Answer 3

Additional formula

• P(A∪B) = P(A) + P(B) - P(A∩B)

Multiplication formula

• P(B|A) = P(A∩B) ÷ P(A)
• P(A∩B) = P(B|A) x P(A)

Question 4

Year 2 - Chapter 2.6

Description of the tree diagram

Answer 4

The first branch simply denotes whether the outcome has, or has not, happened. The probabilites on the second set of branches represent the conditional probabilities of B given that A has, or has not, happened.