# WST02/01 June 2015

> WST02/01 June 2015: 7 questions, 75 marks. Difficulty 0.41, deviation 0.12, algebraic 0.36, text density 0.44. Edexcel IAL Mathematics S2.

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Edexcel IAL · Mathematics · 2015 June

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=ae214267-9f21-476b-9f6d-b700763fb73b)
- [All S2 papers](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/)

Core finding

**WST02/01 June 2015 is a past paper for Edexcel IAL Statistics 2 (WST02), with 7 questions worth 75 marks.** Its mark-weighted Difficulty Measure is 0.41 on a 0.20–0.75 scale, with a Difficulty Deviation of 0.12 and a mark split of 20.0% Easy, 76.0% Medium and 4.0% Hard. Algebraic complexity averages 0.36; text density and modelling average 0.44. All five measures use 23 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 23 parts carrying 75 part marks. Difficulty tags cover 23 parts, algebraic tags 23 and text-density tags 23. Tags are internal metadata, not official exam-board ratings.

- **Difficulty Measure**: 0.41 — 0.20–0.75 · nearer Medium
- **Difficulty Deviation**: 0.12 — 0 = uniform; higher = more mixed
- **Difficulty Ratio**: 20.0 / 76.0 / 4.0 — % Easy / Medium / Hard
- **Algebraic Complexity Measure**: 0.36 — 0.20–0.75 · nearer Medium
- **Text Density and Modelling Measure**: 0.44 — 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** | 0.41 | Σ(d_i × w_i) / Σw_i, with d = 0.20 / 0.45 / 0.75 |
| **Difficulty Deviation** | 0.12 | √(Σw_i(d_i − μ)^2 / Σw_i) |
| **Difficulty Ratio** | 20.0% Easy / 76.0% Medium / 4.0% Hard | marks in band / all tagged marks |
| **Algebraic Complexity Measure** | 0.36 | Σ(c_i × marks_i) / Σmarks_i, with c = 0.20 / 0.45 / 0.75 |
| **Text Density and Modelling Measure** | 0.44 | 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 | [2. Continuous random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-random-variables/) | 10 | 0.40 Medium | 0.40 Medium | 0.20 Low | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ae214267-9f21-476b-9f6d-b700763fb73b&question_id=2fa9bcba-43b1-4ae0-8361-d5c00379d627&source_detail=WST02%2F01+June+2015) |
| **Q2** FRQ | [1. The Binomial and Poisson distributions](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/the-binomial-and-poisson-distributions/) | 15 | 0.42 Medium | 0.42 Medium | 0.55 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ae214267-9f21-476b-9f6d-b700763fb73b&question_id=3916b758-babb-41e6-96ad-c1eec2069854&source_detail=WST02%2F01+June+2015) |
| **Q3** FRQ | [2. Continuous random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-random-variables/) | 11 | 0.40 Medium | 0.34 Medium | 0.53 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ae214267-9f21-476b-9f6d-b700763fb73b&question_id=b8282d5e-b562-42b2-903e-c5c4019bf77b&source_detail=WST02%2F01+June+2015) |
| **Q4** FRQ | [4. Hypothesis tests](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/hypothesis-tests/) | 5 | 0.53 Medium | 0.20 Low | 0.63 High | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ae214267-9f21-476b-9f6d-b700763fb73b&question_id=61cd71ce-3590-46fe-a9fb-309de0a1b3c4&source_detail=WST02%2F01+June+2015) |
| **Q5** FRQ | [4. Hypothesis tests](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/hypothesis-tests/) | 9 | 0.34 Medium | 0.34 Medium | 0.39 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ae214267-9f21-476b-9f6d-b700763fb73b&question_id=a719e780-7fdf-44f6-b34b-6f6ba8f08336&source_detail=WST02%2F01+June+2015) |
| **Q6** FRQ | [1. The Binomial and Poisson distributions](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/the-binomial-and-poisson-distributions/) | 15 | 0.42 Medium | 0.30 Low | 0.55 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ae214267-9f21-476b-9f6d-b700763fb73b&question_id=9265392a-d6c2-4aaf-8ba9-629be4e2ace5&source_detail=WST02%2F01+June+2015) |
| **Q7** FRQ | [2. Continuous random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-random-variables/) | 10 | 0.42 Medium | 0.42 Medium | 0.20 Low | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ae214267-9f21-476b-9f6d-b700763fb73b&question_id=f5f3c1a2-6238-4159-ae75-f6d966ac124f&source_detail=WST02%2F01+June+2015) |

## Topics in this paper

- [2. Continuous random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-random-variables/)
- [1. The Binomial and Poisson distributions](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/the-binomial-and-poisson-distributions/)
- [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-wst02/2015-january-wst02-01/) — January 2015 — 7 questions · 75 marks — Free
- [WST02/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2016-october-wst02-01/) — October 2016 — 7 questions · 75 marks — Free
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- [WST02/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2016-january-wst02-01/) — January 2016 — 7 questions · 75 marks — Free
- [WST02/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2014-june-wst02-01/) — June 2014 — 7 questions · 75 marks — Free
- [WST02/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2014-january-wst02-01/) — January 2014 — 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 0.41 from 23 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 0.12, 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 20.0% Easy, 76.0% Medium and 4.0% 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-wst02/2015-june-wst02-01/