# WST02/01 January 2015

> WST02/01 January 2015: 7 questions, 75 marks. Difficulty 0.46, deviation 0.21, algebraic 0.39, text density 0.47. Edexcel IAL Mathematics S2.

- Canonical HTML: https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2015-january-wst02-01/
- Markdown mirror: https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2015-january-wst02-01/index.md

---

Edexcel IAL · Mathematics · 2015 January

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=ea779e7a-1d7e-4840-bafb-967456a86efc)
- [All S2 papers](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/)

Core finding

**WST02/01 January 2015 is a past paper for Edexcel IAL Statistics 2 (WST02), with 7 questions worth 75 marks.** Its mark-weighted Difficulty Measure is 0.46 on a 0.20–0.75 scale, with a Difficulty Deviation of 0.21 and a mark split of 28.0% Easy, 34.7% Medium and 37.3% Hard. Algebraic complexity averages 0.39; text density and modelling average 0.47. All five measures use 24 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 24 parts carrying 75 part marks. Difficulty tags cover 24 parts, algebraic tags 24 and text-density tags 24. Tags are internal metadata, not official exam-board ratings.

- **Difficulty Measure**: 0.46 — 0.20–0.75 · nearer Medium
- **Difficulty Deviation**: 0.21 — 0 = uniform; higher = more mixed
- **Difficulty Ratio**: 28.0 / 34.7 / 37.3 — % Easy / Medium / Hard
- **Algebraic Complexity Measure**: 0.39 — 0.20–0.75 · nearer Medium
- **Text Density and Modelling Measure**: 0.47 — 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** | 0.46 | Σ(d_i × w_i) / Σw_i, with d = 0.20 / 0.45 / 0.75 |
| **Difficulty Deviation** | 0.21 | √(Σw_i(d_i − μ)^2 / Σw_i) |
| **Difficulty Ratio** | 28.0% Easy / 34.7% Medium / 37.3% Hard | marks in band / all tagged marks |
| **Algebraic Complexity Measure** | 0.39 | Σ(c_i × marks_i) / Σmarks_i, with c = 0.20 / 0.45 / 0.75 |
| **Text Density and Modelling Measure** | 0.47 | 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/) | 16 | 0.47 Medium | 0.36 Medium | 0.45 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ea779e7a-1d7e-4840-bafb-967456a86efc&question_id=0899c35c-f6cb-4384-8e63-9c9450ee04ab&source_detail=WST02%2F01+January+2015) |
| **Q2** FRQ | [2. Continuous random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-random-variables/) | 11 | 0.27 Easy | 0.27 Low | 0.20 Low | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ea779e7a-1d7e-4840-bafb-967456a86efc&question_id=242d83e7-8bf4-4010-b40d-df5bc6c2afbf&source_detail=WST02%2F01+January+2015) |
| **Q3** FRQ | [4. Hypothesis tests](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/hypothesis-tests/) | 11 | 0.49 Medium | 0.36 Medium | 0.40 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ea779e7a-1d7e-4840-bafb-967456a86efc&question_id=f8be0cf7-b208-48f4-9bd7-be56358a1145&source_detail=WST02%2F01+January+2015) |
| **Q4** FRQ | [1. The Binomial and Poisson distributions](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/the-binomial-and-poisson-distributions/) | 7 | 0.34 Medium | 0.20 Low | 0.62 High | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ea779e7a-1d7e-4840-bafb-967456a86efc&question_id=51da8f76-29c0-4ce2-9ff9-6f00e9e44159&source_detail=WST02%2F01+January+2015) |
| **Q5** FRQ | [2. Continuous random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-random-variables/) | 9 | 0.70 Hard | 0.69 High | 0.42 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ea779e7a-1d7e-4840-bafb-967456a86efc&question_id=68d0297d-c66d-4bb1-abe5-1a33323eaff2&source_detail=WST02%2F01+January+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/) | 13 | 0.42 Medium | 0.26 Low | 0.58 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ea779e7a-1d7e-4840-bafb-967456a86efc&question_id=ebb2d8e2-1d1b-4682-bf0d-3ad3a496175b&source_detail=WST02%2F01+January+2015) |
| **Q7** FRQ | [3. Continuous distributions](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-distributions/) | 8 | 0.75 Hard | 0.75 High | 0.75 High | [Go to Practice Hub](https://www.examsci.com/practice?set_id=ea779e7a-1d7e-4840-bafb-967456a86efc&question_id=22bdd5a2-7cf8-4d1a-ad14-a908fb8e2bb9&source_detail=WST02%2F01+January+2015) |

## 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/)
- [3. Continuous distributions](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-distributions/)
- [2. Continuous random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-2-wst02/continuous-random-variables/)
- [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-june-wst02-01/) — June 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
- [WST02/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2016-june-wst02-01/) — June 2016 — 7 questions · 75 marks — Free
- [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 0.46 from 24 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 0.21, 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 28.0% Easy, 34.7% Medium and 37.3% 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.

---

Full page with native tables, bar charts and Practice Hub links: https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-2-wst02/2015-january-wst02-01/