Combined events
Groups
Exclusive events and the OR rule
Events that cannot both happen, the addition rule, and correcting for overlap.
Independence and the AND rule
Independent events, the multiplication rule, and deciding which rule fits.
Dependent events and replacement
The second pick when the first is not put back, and the recalculated fractions.
Conditional probability
Higher only: given-that probability from two-way tables, Venn and tree diagrams.