The Unit 6 paper: what is new at A2

The paper

• WBI16/01, 1 hour 20 minutes, 50 marks, calculator allowed; 20% of the International A2 and 10% of the full International A level.
• Contexts: core practicals 10 to 18 (Units 4 and 5), plus synoptic questions that can draw on any topic and any earlier practical (the January 2024 paper opened with antibacterial plant extracts, an AS core practical).
• Typical structure: two or three short data questions and one long planning question worth around 20 marks (safety, preliminary work, a detailed method, recording and analysis, limitations).

What Unit 6 adds to Unit 3

The planning list adds:

• identify apparatus giving details (range, resolution, dimensions);
• formulate a null hypothesis;
• discuss calibration of instruments;
• identify ethical issues with living organisms.

The analysis list adds tables with units, graphs that could be logarithmic, determining a constant from a graph, and correcting wrong units or significant figures in a table. The maths skills include choosing and using a statistical test: chi-squared, Student's t-test or a correlation coefficient (Spearman's rank in Pearson papers). Formulae and critical values are printed in the question.

Examiner advice

From the January 2024 report:

• Read the whole question and make sure every part is answered.
• Tie answers to the specific investigation, not generic points.
• Do the core practicals yourself so you know where they go wrong.
• Think about how the volumes, concentrations and times in a method were chosen (preliminary work).
• Practise writing null hypotheses even when no test is set.
• Choose a test that suits the data you would actually collect.

Worked example

A Unit 6 planning question says 'Devise an investigation to test the hypothesis that increasing gibberellin concentration increases amylase production in germinating barley.' List the sections a full answer should cover.

1. Safety: hazards such as iodine solution and sterilising agents, with precautions.
2. Preliminary work: find a suitable range of gibberellin concentrations and incubation time.
3. Method: IV values, DV and how measured, controlled variables with methods, repeats, control.
4. Recording and analysis: table, graph, a correlation test with a null hypothesis.
5. Limitations of the method.

Answer: Safety, preliminary work, a detailed controlled method, how results are recorded, presented and tested statistically, and limitations.

Check yourself

1. How many marks is the WBI16 paper worth?
   Show answer

   50. WBI16/01 is a 50-mark, 1 hour 20 minute paper.

2. Which core practicals provide the main contexts for Unit 6?
   • Core practicals 1 to 9 only
   • No core practicals are used
   • Core practicals 5 to 9 only
   • Core practicals 10 to 18, from Units 4 and 5
   Show answer

   Core practicals 10 to 18, from Units 4 and 5. Unit 6 is the A2 practical paper, though synoptic questions can use earlier practicals.

3. Which planning skill is assessed in Unit 6 but not listed in Unit 3?
   • Identifying the dependent variable
   • Formulating a null hypothesis
   • Identifying health and safety issues
   • Discussing whether repeats are appropriate
   Show answer

   Formulating a null hypothesis. Null hypotheses, calibration and ethics are added at A2.

4. Which statistical tests are named in the IAL Biology mathematical skills?
   • ANOVA and regression only
   • Mann-Whitney U only
   • Chi-squared, Student's t-test and a correlation coefficient
   • No tests are required
   Show answer

   Chi-squared, Student's t-test and a correlation coefficient. Appendix 6 skill A.1.9 names these three; Pearson papers use Spearman's rank for correlation.

5. In the exam, how are formulae and critical values for statistical tests provided?
   • They are printed in the question
   • You must memorise every critical value
   • They are on a separate formula booklet you bring
   • They are not needed because only conclusions are asked
   Show answer

   They are printed in the question. Pearson prints the formula and the table in the question; you must know how to use them.

6. What does it mean that Unit 6 is synoptic?
   • It only tests Unit 5
   • It has no calculations
   • Questions can draw on content and practicals from all units
   • It is marked by the teacher
   Show answer

   Questions can draw on content and practicals from all units. Any topic may appear.

Practise with instant feedback Print this lesson

Sources

• Pearson Edexcel International Advanced Level in Biology specification (XBI11/YBI11, first teaching 2018): Unit 3, Unit 6 and Appendix 6 mathematical skills
• Pearson Examiners' Report WBI16/01, January 2024

Last updated 8 November 2026. Spotted a mistake? Tell us.