Edexcel IAL S1 Probability Questions
Venn diagrams, tree diagrams, mutually exclusive vs independent events, conditional probability P(A|B).
- S1 · Statistics 1
- Calculator allowed
- 35 practice questions
What the questions test
The 35 S1 probability practice questions cover:
Worked example 1
A bag contains 5 green counters and 3 yellow counters. A counter is drawn at random, its colour is noted, and it is replaced. This is done 3 times in total. Find the probability that exactly 2 green counters are drawn.
Mark scheme
- M1 for identifying the 3 ways to draw exactly 2 green counters: GGY, GYG, YGG.
- M1 for calculating the probability of one such arrangement, e.g., $(\frac{5}{8}) \times (\frac{5}{8}) \times (\frac{3}{8}) = \frac{75}{512}$.
- A1 for multiplying by 3 to find the total probability: $\frac{225}{512}$.
Worked example 2
Three independent events $A$, $B$, and $C$ have probabilities $P(A) = 0.5$, $P(B) = 0.4$, and $P(C) = 0.3$. Find the probability that exactly one of these events occurs.
Mark scheme
- M1 for identifying the three scenarios: $(A \cap B' \cap C')$, $(A' \cap B \cap C')$, and $(A' \cap B' \cap C)$.
- M1 for calculating the probabilities of these scenarios: $(0.5\times0.6\times0.7) + (0.5\times0.4\times0.7) + (0.5\times0.6\times0.3)$.
- A1 for evaluating and summing: $0.21 + 0.14 + 0.09 = 0.44$.
FAQ
What probability is in Edexcel IAL S1?
Venn diagrams, tree diagrams, mutually exclusive vs independent events, conditional probability P(A|B).
Is S1 a calculator paper?
Yes, a calculator is allowed in S1, but method marks are only given for working you write down.
How are S1 probability questions marked?
With M marks for a correct method, A marks for accurate answers that depend on the M mark before them, and B marks for independent results, as in the worked examples on this page.