# WST02/01 October 2019

> WST02/01 October 2019: 7 questions, 75 marks. Difficulty 0.45, deviation 0.19, algebraic 0.34, text density 0.48. Edexcel IAL Mathematics S2.

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Edexcel IAL · Mathematics · 2019 October

This Statistics 2 (WST02) paper contains 7 questions worth 75 marks. The profile below reports five mark-weighted difficulty and complexity measures, and every question row repeats them. Full question text and mark scheme open in the Interactive Practice Hub.

- Edexcel IAL
- S2
- 7 questions
- 75 marks
- Free paper
- [Practise this paper](https://www.examsci.com/practice?set_id=07694c98-38fb-461c-aaf2-5b1b89a8e110)
- [All S2 papers](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/)

Core finding

**WST02/01 October 2019 is a past paper for Edexcel IAL Statistics 2 (WST02), with 7 questions worth 75 marks.** Its mark-weighted Difficulty Measure is 0.45 on a 0.20–0.75 scale, with a Difficulty Deviation of 0.19 and a mark split of 24.0% Easy, 44.0% Medium and 32.0% Hard. Algebraic complexity averages 0.34; text density and modelling average 0.48. All five measures use 21 part-level tags, not candidate results. Every question row below repeats them and opens the Interactive Practice Hub for that question.

## Difficulty & complexity profile

All five measures are mark-weighted and calculated from 21 parts carrying 75 part marks. Difficulty tags cover 21 parts, algebraic tags 21 and text-density tags 21. Tags are internal metadata, not official exam-board ratings.

- **Difficulty Measure**: 0.45 — 0.20–0.75 · nearer Medium
- **Difficulty Deviation**: 0.19 — 0 = uniform; higher = more mixed
- **Difficulty Ratio**: 24.0 / 44.0 / 32.0 — % Easy / Medium / Hard
- **Algebraic Complexity Measure**: 0.34 — 0.20–0.75 · nearer Medium
- **Text Density and Modelling Measure**: 0.48 — 0.20–0.75 · nearer Medium

Scale: Easy 0.20 · Medium 0.45 · Hard 0.75, and Low 0.20 · Medium 0.45 · High 0.75 for the two complexity measures. [How each band is defined and how the values are calculated →](https://www.examsci.com/guides/difficulty-and-complexity-measures/)

### Definitions and calculation

| Measure | Paper value | Formula |
| --- | --- | --- |
| **Difficulty Measure** | 0.45 | Σ(d_i × w_i) / Σw_i, with d = 0.20 / 0.45 / 0.75 |
| **Difficulty Deviation** | 0.19 | √(Σw_i(d_i − μ)^2 / Σw_i) |
| **Difficulty Ratio** | 24.0% Easy / 44.0% Medium / 32.0% Hard | marks in band / all tagged marks |
| **Algebraic Complexity Measure** | 0.34 | Σ(c_i × marks_i) / Σmarks_i, with c = 0.20 / 0.45 / 0.75 |
| **Text Density and Modelling Measure** | 0.48 | Σ(t_i × marks_i) / Σmarks_i, with t = 0.20 / 0.45 / 0.75 |

w_i equals the part marks, except for a Hard part worth 4 or more marks, where w_i = marks^0.75 to offset the accessible starter steps inside long structured questions.

## Question list

Each measure is recalculated from the parts of that question and uses the same weights as the paper profile.

| Question | Topic | Marks | Difficulty Measure | Algebraic Complexity Measure | Text Density and Modelling Measure | Practice |
| --- | --- | --- | --- | --- | --- | --- |
| **Q1** FRQ | [1. The Binomial and Poisson distributions](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/the-binomial-and-poisson-distributions/) | 9 | 0.37 Medium | 0.39 Medium | 0.45 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=07694c98-38fb-461c-aaf2-5b1b89a8e110&question_id=6bdb1b8e-afbc-494d-9b94-70cf20c5d0be&source_detail=WST02%2F01+October+2019) |
| **Q2** FRQ | [2. Continuous random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-random-variables/) | 9 | 0.34 Medium | 0.34 Medium | 0.34 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=07694c98-38fb-461c-aaf2-5b1b89a8e110&question_id=d72928ea-7d36-47af-86bb-8adc7da8f87a&source_detail=WST02%2F01+October+2019) |
| **Q3** FRQ | [1. The Binomial and Poisson distributions](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/the-binomial-and-poisson-distributions/) | 12 | 0.45 Medium | 0.35 Medium | 0.63 High | [Go to Practice Hub](https://www.examsci.com/practice?set_id=07694c98-38fb-461c-aaf2-5b1b89a8e110&question_id=206a25d4-6cfd-47fb-b9a9-90e04f28e645&source_detail=WST02%2F01+October+2019) |
| **Q4** FRQ | [2. Continuous random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-random-variables/) | 14 | 0.49 Medium | 0.41 Medium | 0.20 Low | [Go to Practice Hub](https://www.examsci.com/practice?set_id=07694c98-38fb-461c-aaf2-5b1b89a8e110&question_id=cd624a04-cc38-45c6-a331-1d55303e1b28&source_detail=WST02%2F01+October+2019) |
| **Q5** FRQ | [4. Hypothesis tests](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/hypothesis-tests/) | 11 | 0.61 Hard | 0.36 Medium | 0.75 High | [Go to Practice Hub](https://www.examsci.com/practice?set_id=07694c98-38fb-461c-aaf2-5b1b89a8e110&question_id=5e6ea7d4-8608-4b5e-8d09-16c4e6d08053&source_detail=WST02%2F01+October+2019) |
| **Q6** FRQ | [3. Continuous distributions](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-distributions/) | 8 | 0.33 Medium | 0.20 Low | 0.45 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=07694c98-38fb-461c-aaf2-5b1b89a8e110&question_id=be489b51-6861-4a73-ab7a-a71593478d97&source_detail=WST02%2F01+October+2019) |
| **Q7** FRQ | [2. Continuous random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-random-variables/) | 12 | 0.55 Medium | 0.28 Low | 0.58 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=07694c98-38fb-461c-aaf2-5b1b89a8e110&question_id=28f278d9-6388-41b7-8995-a1a0598de14b&source_detail=WST02%2F01+October+2019) |

## Topics in this paper

- [1. The Binomial and Poisson distributions](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/the-binomial-and-poisson-distributions/)
- [2. Continuous random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-random-variables/)
- [3. Continuous distributions](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-distributions/)
- [4. Hypothesis tests](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/hypothesis-tests/)

## Related papers

- [WST02/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2019-june-wst02-01/) — June 2019 — 7 questions · 75 marks — Free
- [WST02/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2019-january-wst02-01/) — January 2019 — 7 questions · 75 marks — Free
- [WST02/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2020-october-wst02-01/) — October 2020 — 6 questions · 75 marks — Free
- [WST02/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2020-january-wst02-01/) — January 2020 — 6 questions · 75 marks — Free
- [WST02/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2018-october-wst02-01/) — October 2018 — 7 questions · 75 marks — Free
- [WST02/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2018-june-wst02-01/) — June 2018 — 7 questions · 75 marks — Free

## Paper FAQ

**How are the difficulty and complexity measures calculated?**

Each part is weighted by its official marks. Difficulty uses Easy 0.20, Medium 0.45 and Hard 0.75; algebraic complexity and text density and modelling use Low 0.20, Medium 0.45 and High 0.75. A Hard part worth 4 or more marks is down-weighted to marks^0.75, so the accessible starter steps inside a long structured question do not inflate the difficulty result. This paper's Difficulty Measure is 0.45 from 21 parts.

**What does the Difficulty Deviation show?**

It is the mark-weighted standard deviation of the part difficulty values around the paper mean. A value of 0 would mean every tagged part has the same difficulty; this paper's deviation is 0.19, so its parts are more mixed than a single-level paper.

**Is the Difficulty Ratio based on question counts or marks?**

It is based on official marks, not question counts. This paper's shares are 24.0% Easy, 44.0% Medium and 32.0% Hard; the three shares sum to 100% before rounding.

**Are these official difficulty ratings?**

No. They are derived from the platform's part-level difficulty and static-question-profile tags. They are not exam-board grade boundaries and are not calculated from candidate outcomes. Use them to compare the demand profile of papers, not to predict a grade.

**Why does each question row show its own measures?**

Each row recalculates the same mark-weighted formula from that question's parts. A single-part MCQ therefore shows the tag value directly, while a multi-part structured question blends the tags of its parts using the same Hard-part decay as the paper profile.

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Full page with native tables, bar charts and Practice Hub links: https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2019-october-wst02-01/