# WST01/01 January 2015

> WST01/01 January 2015: 7 questions, 75 marks. Difficulty 0.32, deviation 0.12, algebraic 0.29, text density 0.35. Edexcel IAL Mathematics S1.

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Edexcel IAL · Mathematics · 2015 January

This Statistics 1 (WST01) 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
- S1
- 7 questions
- 75 marks
- Free paper
- [Practise this paper](https://www.examsci.com/practice?set_id=675a8bc9-486a-4943-956c-2e59b4607250)
- [All S1 papers](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-1-wst01/)

Core finding

**WST01/01 January 2015 is a past paper for Edexcel IAL Statistics 1 (WST01), with 7 questions worth 75 marks.** Its mark-weighted Difficulty Measure is 0.32 on a 0.20–0.75 scale, with a Difficulty Deviation of 0.12 and a mark split of 52.0% Easy, 48.0% Medium and 0.0% Hard. Algebraic complexity averages 0.29; text density and modelling average 0.35. All five measures use 34 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 34 parts carrying 75 part marks. Difficulty tags cover 34 parts, algebraic tags 34 and text-density tags 34. Tags are internal metadata, not official exam-board ratings.

- **Difficulty Measure**: 0.32 — 0.20–0.75 · nearer Easy
- **Difficulty Deviation**: 0.12 — 0 = uniform; higher = more mixed
- **Difficulty Ratio**: 52.0 / 48.0 / 0.0 — % Easy / Medium / Hard
- **Algebraic Complexity Measure**: 0.29 — 0.20–0.75 · nearer Low
- **Text Density and Modelling Measure**: 0.35 — 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** | 0.32 | 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** | 52.0% Easy / 48.0% Medium / 0.0% Hard | marks in band / all tagged marks |
| **Algebraic Complexity Measure** | 0.29 | Σ(c_i × marks_i) / Σmarks_i, with c = 0.20 / 0.45 / 0.75 |
| **Text Density and Modelling Measure** | 0.35 | 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 | [5. Discrete random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-1-wst01/discrete-random-variables/) | 10 | 0.33 Medium | 0.28 Low | 0.33 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=675a8bc9-486a-4943-956c-2e59b4607250&question_id=c31727c3-b189-494c-9c70-1f6cbffff54c&source_detail=WST01%2F01+January+2015) |
| **Q2** FRQ | [2. Representation and summary of data](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-1-wst01/representation-and-summary-of-data/) | 9 | 0.34 Medium | 0.20 Low | 0.45 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=675a8bc9-486a-4943-956c-2e59b4607250&question_id=8e434ca4-43ef-43d3-b250-004ebaae1ca2&source_detail=WST01%2F01+January+2015) |
| **Q3** FRQ | [4. Correlation and regression](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-1-wst01/correlation-and-regression/) | 9 | 0.26 Easy | 0.20 Low | 0.45 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=675a8bc9-486a-4943-956c-2e59b4607250&question_id=1d421690-35fe-4ae4-8040-4ec71ee105e6&source_detail=WST01%2F01+January+2015) |
| **Q4** FRQ | [3. Probability](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-1-wst01/probability/) | 9 | 0.34 Medium | 0.34 Medium | 0.20 Low | [Go to Practice Hub](https://www.examsci.com/practice?set_id=675a8bc9-486a-4943-956c-2e59b4607250&question_id=a5b1ca16-1bae-4aa1-930e-6c95e1ad2d25&source_detail=WST01%2F01+January+2015) |
| **Q5** FRQ | [4. Correlation and regression](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-1-wst01/correlation-and-regression/) | 13 | 0.28 Easy | 0.28 Low | 0.45 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=675a8bc9-486a-4943-956c-2e59b4607250&question_id=10bcd88d-ff09-4ca1-b234-a2fe2ea20fe6&source_detail=WST01%2F01+January+2015) |
| **Q6** FRQ | [5. Discrete random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-1-wst01/discrete-random-variables/) | 14 | 0.34 Medium | 0.34 Medium | 0.20 Low | [Go to Practice Hub](https://www.examsci.com/practice?set_id=675a8bc9-486a-4943-956c-2e59b4607250&question_id=85e874b3-f78a-492d-b7bd-ced901a8b9eb&source_detail=WST01%2F01+January+2015) |
| **Q7** FRQ | [6. The Normal distribution](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-1-wst01/the-normal-distribution/) | 11 | 0.36 Medium | 0.36 Medium | 0.43 Medium | [Go to Practice Hub](https://www.examsci.com/practice?set_id=675a8bc9-486a-4943-956c-2e59b4607250&question_id=f64c2c5b-81bf-4628-ba99-c2a5d582abfc&source_detail=WST01%2F01+January+2015) |

## Topics in this paper

- [5. Discrete random variables](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-1-wst01/discrete-random-variables/)
- [3. Probability](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-1-wst01/probability/)
- [2. Representation and summary of data](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-1-wst01/representation-and-summary-of-data/)
- [6. The Normal distribution](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-1-wst01/the-normal-distribution/)
- [4. Correlation and regression](https://www.examsci.com/topics/edexcel-ial/mathematics/statistics-1-wst01/correlation-and-regression/)

## Related papers

- [WST01/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-1-wst01/2015-june-wst01-01/) — June 2015 — 8 questions · 75 marks — Free
- [WST01/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-1-wst01/2016-october-wst01-01/) — October 2016 — 6 questions · 75 marks — Free
- [WST01/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-1-wst01/2016-june-wst01-01/) — June 2016 — 7 questions · 75 marks — Free
- [WST01/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-1-wst01/2016-january-wst01-01/) — January 2016 — 6 questions · 75 marks — Free
- [WST01/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-1-wst01/2014-june-wst01-01/) — June 2014 — 7 questions · 75 marks — Free
- [WST01/01](https://www.examsci.com/past-papers/edexcel-ial/mathematics/statistics-1-wst01/2014-january-wst01-01/) — January 2014 — 8 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 0.32 from 34 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 52.0% Easy, 48.0% Medium and 0.0% 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-1-wst01/2015-january-wst01-01/