| Exam Board | Edexcel |
|---|---|
| Module | S1 (Statistics 1) |
| Year | 2024 |
| Session | June |
| Marks | 13 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Principle of Inclusion/Exclusion |
| Type | Three-Set Venn Diagram Probability Calculation |
| Difficulty | Standard +0.3 This is a standard S1 Venn diagram question with straightforward probability calculations. Part (a) requires simple addition of regions, (b)-(c) use independence to set up basic equations, and (d)-(e) involve routine probability operations. While multi-part, each step follows directly from definitions without requiring novel insight or complex problem-solving. |
| Spec | 2.03a Mutually exclusive and independent events2.03b Probability diagrams: tree, Venn, sample space2.03c Conditional probability: using diagrams/tables2.03d Calculate conditional probability: from first principles |
| Answer | Marks | Guidance |
|---|---|---|
| Answer/Working | Mark | Guidance |
| 0.16 oe | B1 | Correct probability |
| Answer | Marks | Guidance |
|---|---|---|
| Answer/Working | Mark | Guidance |
| \([P(C)=] 0.04+0.15+0.12+p [=0.31+p]\); \([P(S)=] 0.1+0.15+0.12+0.23[=0.6]\); \([P(S \cap C)=] 0.15+0.12[=0.27]\) | M1 | For 2 correct probability expressions |
| All three expressions correct; \([P(C')=] 0.1+0.23+q[=0.33+q]\); \([P(S')=]0.4\); \([P(S'\cap C')=]q\) | M1 | All 3 correct probability expressions; allow \(P(C)=0.45\) |
| \((\text{"0.31"}+p)\times\text{"0.6"} = \text{"0.27"}\) oe; or \((\text{"0.33"}+q)\times\text{"0.4"} = q\) oe | M1d | Dependent on 1st M1; for use of \(P(C\cap S)=P(C)\times P(S)\) or \(P(C'\cap S')=P(C')\times P(S')\) ft their probabilities if labelled clearly |
| \(p = 0.14\) oe; \(q = 0.22\) oe | A1 | For 0.14 or exact equivalent or 0.22 or exact equivalent |
| Answer | Marks | Guidance |
|---|---|---|
| Answer/Working | Mark | Guidance |
| \(q = 1-(0.04+0.12+0.15+0.1+0.23+\text{"p"})\); or \(p = 1-(0.04+0.12+0.15+0.1+0.23+\text{"q"})\) | M1 | For correct expression for \(q\) ft their \(p\) or correct expression for \(p\) ft their \(q\) |
| \(q = 0.22\) oe; \(p = 0.14\) oe | A1ft | For 0.22 or exact equivalent ft their \(p\), or 0.14 or exact equivalent ft their \(q\) (\(p+q=0.36\) provided \(p\) and \(q\) are probabilities) |
| Answer | Marks | Guidance |
|---|---|---|
| Answer/Working | Mark | Guidance |
| \([P((C \cup S) \cap G')] = 0.39\) oe | B1 | For 0.39 or exact equivalent; do not allow \(0.04+0.12+0.23\) |
| Answer | Marks | Guidance |
|---|---|---|
| Answer/Working | Mark | Guidance |
| \(P(C \mid (S \cap G)) = \frac{0.15}{0.15+0.1}\) | M1 | For \(\frac{0.15}{0.15+0.1}\) |
| \(= 0.6\) oe | A1 | For 0.6 or exact equivalent |
| Answer | Marks | Guidance |
|---|---|---|
| Answer/Working | Mark | Guidance |
| Number of teenagers \(= \frac{76}{0.15+\text{"p"}}\) oe | M1 | Relating 76 to their \(P(C \cap G)\); may be implied by awrt 262 |
| Number who don't play Scrabble \(= \text{"}\!\left(\frac{76}{0.15+p}\right)\!\text{"} \times 0.4\ (= 104.8\ldots)\) | M1 | For number of teenagers \(\times 0.4\) ft their number of teenagers e.g. \(0.4 \times \text{"262"}\); provided number of teenagers is not 76 |
| \(= 104.8\ldots\) awrt 105 | A1 | awrt 105 ISW |
# Question 6:
## Part (a):
| Answer/Working | Mark | Guidance |
|---|---|---|
| 0.16 oe | B1 | Correct probability |
## Part (b):
| Answer/Working | Mark | Guidance |
|---|---|---|
| $[P(C)=] 0.04+0.15+0.12+p [=0.31+p]$; $[P(S)=] 0.1+0.15+0.12+0.23[=0.6]$; $[P(S \cap C)=] 0.15+0.12[=0.27]$ | M1 | For 2 correct probability expressions |
| All three expressions correct; $[P(C')=] 0.1+0.23+q[=0.33+q]$; $[P(S')=]0.4$; $[P(S'\cap C')=]q$ | M1 | All 3 correct probability expressions; allow $P(C)=0.45$ |
| $(\text{"0.31"}+p)\times\text{"0.6"} = \text{"0.27"}$ oe; or $(\text{"0.33"}+q)\times\text{"0.4"} = q$ oe | M1d | Dependent on 1st M1; for use of $P(C\cap S)=P(C)\times P(S)$ or $P(C'\cap S')=P(C')\times P(S')$ ft their probabilities if labelled clearly |
| $p = 0.14$ oe; $q = 0.22$ oe | A1 | For 0.14 or exact equivalent or 0.22 or exact equivalent |
## Part (c):
| Answer/Working | Mark | Guidance |
|---|---|---|
| $q = 1-(0.04+0.12+0.15+0.1+0.23+\text{"p"})$; or $p = 1-(0.04+0.12+0.15+0.1+0.23+\text{"q"})$ | M1 | For correct expression for $q$ ft their $p$ or correct expression for $p$ ft their $q$ |
| $q = 0.22$ oe; $p = 0.14$ oe | A1ft | For 0.22 or exact equivalent ft their $p$, or 0.14 or exact equivalent ft their $q$ ($p+q=0.36$ provided $p$ and $q$ are probabilities) |
## Part (d)(i):
| Answer/Working | Mark | Guidance |
|---|---|---|
| $[P((C \cup S) \cap G')] = 0.39$ oe | B1 | For 0.39 or exact equivalent; do not allow $0.04+0.12+0.23$ |
## Part (d)(ii):
| Answer/Working | Mark | Guidance |
|---|---|---|
| $P(C \mid (S \cap G)) = \frac{0.15}{0.15+0.1}$ | M1 | For $\frac{0.15}{0.15+0.1}$ |
| $= 0.6$ oe | A1 | For 0.6 or exact equivalent |
## Part (e):
| Answer/Working | Mark | Guidance |
|---|---|---|
| Number of teenagers $= \frac{76}{0.15+\text{"p"}}$ oe | M1 | Relating 76 to their $P(C \cap G)$; may be implied by awrt 262 |
| Number who don't play Scrabble $= \text{"}\!\left(\frac{76}{0.15+p}\right)\!\text{"} \times 0.4\ (= 104.8\ldots)$ | M1 | For number of teenagers $\times 0.4$ ft their number of teenagers e.g. $0.4 \times \text{"262"}$; provided number of teenagers is not 76 |
| $= 104.8\ldots$ awrt 105 | A1 | awrt 105 ISW |
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\begin{enumerate}
\item The Venn diagram shows the probabilities related to teenagers playing 3 particular board games.\\
$C$ is the event that a teenager plays Chess\\
$S$ is the event that a teenager plays Scrabble\\
$G$ is the event that a teenager plays Go\\
where $p$ and $q$ are probabilities.\\
\includegraphics[max width=\textwidth, alt={}, center]{ee0c7c12-84f3-479c-b36a-3357f8529a1c-22_684_935_598_566}\\
(a) Find the probability that a randomly selected teenager plays Chess but does not play Go.
\end{enumerate}
Given that the events $C$ and $S$ are independent,\\
(b) find the value of $p$\\
(c) Hence find the value of $q$\\
(d) Find (i) $\mathrm { P } \left( ( C \cup S ) \cap G ^ { \prime } \right)$\\
(ii) $\mathrm { P } ( C \mid ( S \cap G ) )$
A youth club consists of a large number of teenagers.\\
In this youth club 76 teenagers play Chess and Go.\\
(e) Use the information in the Venn diagram to estimate how many of the teenagers in the youth club do not play Scrabble.
\hfill \mbox{\textit{Edexcel S1 2024 Q6 [13]}}