Edexcel IAL S1 June 2024 mark scheme and question paper (WST01/01)

3 S1 questions like these, with worked solutions

Written and checked by us, not taken from the Pearson paper. Try each one, then tap "Worked solution" to see every step and its marks.

1. Correlation and Regression · 4 marks

   Using the summary statistics $\sum x=140$, $\sum y=200$, $S_{xx}=270$, $S_{xy}=-300$, and $n=20$, find the equation of the regression line of $y$ on $x$ in the form $y=a+bx$.

   Worked solution

   1. M1 for calculating the gradient $b=\frac{S_{xy}}{S_{xx}}=\frac{-300}{270}$.
   2. A1 for $b=-\frac{10}{9}$ or $\approx -1.11$.
   3. M1 for calculating the means $\overline{x}=7$, $\overline{y}=10$, and determining the intercept $a=10-(-\frac{10}{9})(7)$.
   4. A1 for final equation $y=17.8-1.11x$ (or $y=\frac{160}{9}-\frac{10}{9}x$).

2. Discrete Random Variables · 5 marks

   A discrete random variable $X$ has $E(X)=2$ and $Var(X)=4$. Another variable is defined as $Y=aX+b$, where $a>0$. Given that $E(Y)=10$ and $Var(Y)=36$, find the values of the constants $a$ and $b$.

   Worked solution

   1. M1 for using the variance property $Var(Y)=a^{2}Var(X)$ to write $36=a^2(4)$.
   2. A1 for solving to find $a^2=9⟹a=3$ (since $a>0$).
   3. M1 for using the expectation property $E(Y)=aE(X)+b$ to write $10=a(2)+b$.
   4. M1 for substituting $a=3$ into the equation: $10=3(2)+b$.
   5. A1 for concluding $b=4$.

3. Normal Distribution · 5 marks

   The random variable $X\sim N(40,{\sigma }^2)$ and $P(X>45)=0.3$.
   (a) Find the value of $\sigma$. (3)
   (b) Hence find $P(X<30)$. (2)

   Worked solution

   1. $P(Z<z)=0.7\Rightarrow z=0.5244$ B1
      $\frac{45-40}{\sigma }=0.5244$ M1
      $\sigma =9.53$ A1

   2. $P(Z<\frac{30-40}{9.53})=P(Z<-1.049)$ M1
      $=0.147$ A1

More on these topics: Correlation and Regression · Discrete Random Variables · Normal Distribution

What's on this paper

What this paper is like

• Shape: 6 questions, 75 marks in 1 h 30 min (about 1.2 minutes a mark); questions from 10 to 14 marks.
• Biggest question: Q3, 14 marks: pebble lengths: grouped data.
• Marks by main topic: Representation of Data 27, Correlation and Regression 13, Probability 13, Discrete Random Variables 12, Normal Distribution 10.
• More Representation of Data in other sittings: October 2024 Q1 (10 marks), January 2024 Q1 (8 marks), October 2023 Q2 (13 marks).
• Against the other 14 sittings we mapped: more marks on Representation of Data (27 marks here, 11 on average); fewer on Measures of Location and Spread (0 marks here, 5 on average).
• Not on this paper: Data and Summary Statistics, Measures of Location and Spread.
• Calculator: allowed.

WST01/01: question by question

Labels and topics are ours, read from the WST01/01 paper (checked 2026-11-01); marks as printed. Tap a number to practise that topic.

1. Q1Birch and maple growth: box plots (13 marks) · S1 Representation of Data, S1 Measures of Location and Spread
2. Q2Spinner scores: distribution and variance (12 marks) · S1 Discrete Random Variables
3. Q3Pebble lengths: grouped data (14 marks) · S1 Representation of Data, S1 Measures of Location and Spread
4. Q4Bear length and girth: regression (13 marks) · S1 Correlation and Regression
5. Q5Normal model for competition times (10 marks) · S1 Normal Distribution
6. Q6Venn diagram of teenagers' sports (13 marks) · S1 Probability

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What the examiners said about this paper

Summarised in our own words from the board's examiner report (Examiner Insights).

• WST01/01: Standardisation not shown when the question requires it (Q5); Outliers (Q1); Comparisons without figures or context (Q1(e)). Official examiner report ↗

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