S1.3 - Probability

Elementary probability.

Use elementary probability to connect the rule to the data and decision in the question.

This matters because elementary probability determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply elementary probability to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: Elementary probability is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Sample space.; Exclusive and Understanding and use of complementary events.; Conditional P(A′) = 1 − P(A), probability.; P(A ∪ B) = P(A) + P(B) − P(A ∩ B), P(A ∩ B) = P(A) P(B | A).

Use sample space to connect the rule to the data and decision in the question.

This matters because sample space determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply sample space to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: Sample space is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Independence of two events.; P(B | A) = P(B), P(A | B) = P(A), P(A ∩ B) = P(A) P(B).

Use independence of two events to connect the rule to the data and decision in the question.

This matters because independence of two events determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply independence of two events to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: Independence of two events is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Sum and product laws.; Use of tree diagrams and Venn diagrams.; Sampling with and without replacement.

Use sum and product laws to connect the rule to the data and decision in the question.

This matters because sum and product laws determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply sum and product laws to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: Sum and product laws is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.