Edexcel IAL S1 January 2025 question paper and mark scheme (WST01/01)

Try 3 S1 questions like these

Written and checked by us, not taken from the Pearson paper. Tap "Worked answer" to see every step.

1. Representation of Data · 5 marks

   The data in a histogram is grouped into classes. A bar representing the class $100 \le x < 150$ has a width of $2.5\text{ cm}$ and a height of $4\text{ cm}$. The total area of all bars in the histogram is $90\text{ cm}^2$. If the bar for $100 \le x < 150$ represents a frequency of $20$, calculate the total frequency of the entire data set.

   Worked answer

   1. M1 for calculating the area of the specified bar: $2.5 \times 4 = 10\text{ cm}^2$.
   2. M1 for establishing the relationship between area and frequency: $10\text{ cm}^2$ represents a frequency of $20$.
   3. A1 for calculating the scale factor: $1\text{ cm}^2$ represents $2$ items (since $20 / 10 = 2$).
   4. M1 for using the total area to find total frequency: $90\text{ cm}^2 \times 2$.
   5. A1 for the final answer: $180$ items.

2. Probability · 3 marks

   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.

   Worked answer

   1. M1 for identifying the 3 ways to draw exactly 2 green counters: GGY, GYG, YGG.
   2. M1 for calculating the probability of one such arrangement, e.g., $(\frac{5}{8}) \times (\frac{5}{8}) \times (\frac{3}{8}) = \frac{75}{512}$.
   3. A1 for multiplying by 3 to find the total probability: $\frac{225}{512}$.

3. 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 answer

   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 $\bar{x} = 7$, $\bar{y} = 10$, and determining the intercept $a = 10 - (-\frac{10}{9})(7)$.
   4. A1 for final equation $y = 17.8 - 1.11x$ (or $y = \frac{160}{9} - \frac{10}{9}x$).

More on these topics: Representation of Data · Probability · Correlation and Regression

S1 topics this paper can test

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• Data and Summary Statistics
• Representation of Data
• Probability
• Correlation and Regression
• Discrete Random Variables
• Normal Distribution
• Measures of Location and Spread

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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); Sxx and Sxy "show that" (Q6); Independent versus mutually exclusive (Q4). Official examiner report ↗

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Formula booklet

Mathematical Formulae and Statistical Tables (International AS/A Level Mathematics) · Pearson Edexcel · For the 2018 IAL specification (current)