Maths · Probability. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
A combined event is two or more things happening, such as rolling two dice or taking two counters. First list every outcome in an organised way: a grid for two dice, a tree diagram for events in stages, a Venn diagram or two-way table for groups that overlap.
Events are independent when one does not change the probability of the other, for example two separate dice rolls. When items are taken without replacement, the events are dependent: the total goes down by one for the second pick, and so does the number of the colour already taken.
A conditional probability is found inside a smaller group. The words 'given that' tell you which group to use as the new total.
Keeping the same probabilities for the second pick when the first item is not put back. After one counter is taken, there is one fewer of that colour and one fewer in total.
Answer: 7/15
Type what you are stuck on. The helper finds the explanation, worked examples and the notes to read, free and instant.
← Probability and expected outcomesSampling and statistical diagrams →Take a Maths test