Edexcel A-Level Biology data sheet: Formulae and definitions explained

Pearson Edexcel A-Level Biology Spec B (9BI0) doesn't publish a standalone data booklet in the way OCR Chemistry does. If you've gone looking for a downloadable Biology data sheet PDF and not found one, that's why. Instead, formulae appear in the question stem on any question that needs them.

This guide covers Edexcel Spec B (9BI0). Edexcel also runs Spec A, officially called Salters-Nuffield Advanced Biology or SNAB (9BN0), which is a different qualification with a different course structure. The two aren't interchangeable, so check which specification your school teaches before using this guide: it should say SNAB or 9BN0 if you're on Spec A, or just 'Edexcel Biology B' or 9BI0 if you're on Spec B.

The formulae and statistical tests you need are listed in Appendix 6 of the Spec B specification ('Mathematical skills and exemplifications'). The piece below walks through everything on the paper, what you still need to memorise, and how the stats tests work.

Edexcel Spec B's maths requirements are set out in Appendix 6 of the specification. The split follows a familiar logic: biology-specific formulae that come up repeatedly in the course get recalled from memory, while formulae that need critical-values tables (every stats test) or that would clutter a question stem get printed on the paper when used.

The tables below list both categories. If you're building a revision card, the recall list is the one that matters most.

Magnification is the main recall item. It appears across Papers 1, 2 and 3 whenever a question works with electron or light-microscope images. Mark schemes are strict on units: if the image is measured in millimetres, convert to micrometres before dividing (1 mm = 1000 μm). An image 15 mm long at × 500 magnification represents a real size of 15 mm / 500 = 0.03 mm = 30 μm.

Cardiac output is the second named exemplar. Appendix 6 A.2.4 (solve algebraic equations in a biological context) uses cardiac output = stroke volume × heart rate as the worked example. The arithmetic is trivial once you know the relationship, and it comes up repeatedly in the cardiovascular and exercise-physiology content.

That's the Spec B exemplar list. Spec B is still lighter on biology-specific recall equations than AQA or OCR, which name a few more memorisation items (NPP = GPP - R, 2ⁿ). On Spec B, you're expected to interpret most other relationships from first principles rather than quote a named formula.

Hardy-Weinberg is listed in Spec B Topic 8 as content you need to apply (analysis of allele frequencies using the Hardy-Weinberg equation). Pearson doesn't publish a guarantee that the equation is printed in the question stem, so don't bank on it: learn both p + q = 1 and p² + 2pq + q² = 1, and know what each term represents (p and q are allele frequencies that sum to 1; p², 2pq and q² are the homozygous dominant, heterozygous, and homozygous recessive genotype frequencies). If the equation is printed in the stem on your paper, that's a bonus; if it isn't, you've still got the recall.

The index of diversity shows up in Spec B Appendix 6 (A.2.3) as 'use of a formula to calculate an index of diversity'. The specific form the spec gives as the exemplar is D = N(N-1) / Σn(n-1), the same canonical form AQA uses in its content section. The formula is provided in the question stem when needed, but learning the Spec-B canonical form makes the arithmetic faster under exam pressure.

Linear-relationship work (y = mx + c, rates of change) is covered in Appendix 6. The equation is given when needed, and the examinable skill is extracting a gradient from a graph and giving it physical meaning (rate, in appropriate units).

Edexcel Spec B lists three statistical tests you can be asked to apply: chi-squared, Student's t-test (of difference), and Spearman's rank correlation coefficient. Each is typically provided with the formula and a critical-values table in the question stem when needed. You pick the right test for the data type, apply it, and compare your test statistic to the critical value at the stated significance level (usually p = 0.05).

Chi-squared is for comparing observed and expected frequencies: the classic use case is a genetic cross testing predicted phenotype ratios. The t-test is for comparing the means of two samples. Spearman's is for correlation between two ranked variables, often from ecology datasets collected along a transect.

Mann-Whitney U and Wilcoxon signed rank are not surfaced in Spec B's Appendix 6 statistical-tests list, so you don't need to drill them for the exam.

Appendix 6 (A.1.10) of the Spec B specification lists standard deviation as an examinable measure of dispersion, with candidates tested on their ability to 'calculate the standard deviation' and understand why it might be a more useful measure than range. In practice this means you need to understand measures of dispersion (standard deviation, range), interpret standard deviation values, and know when standard deviation is a more useful summary than range.

The formula is typically provided on the paper when a mechanical calculation is set. The testable skill is interpretation: knowing what a standard deviation of 2.3 tells you about the spread of a dataset compared with a standard deviation of 0.5, judging whether two means are significantly different by looking at the overlap of error bars (which usually represent one standard deviation above and below the mean), and spotting when a mean is misleading because the standard deviation is large relative to it.

This is a slightly different position from AQA, which explicitly rules out standard-deviation calculation on written papers (section 3.4.7). On Edexcel Spec B you can be set a calculation (with the formula given); on AQA you only interpret.

All three major boards (AQA, Edexcel, OCR) use the embedded-formulae approach for Biology rather than publishing a separate data booklet. But the detail differs enough to matter.

Edexcel Spec B's named exemplar recall list is short: magnification plus cardiac output = stroke volume × heart rate (Appendix 6 A.2.4). The Hardy-Weinberg equations sit on top of that as Topic 8 content that isn't guaranteed to be printed in the stem, so Edexcel students should treat them as recall too. AQA's recall list is broader (magnification, cardiac output, 2ⁿ, NPP = GPP - R, N = I - (F + R), plus Hardy-Weinberg, which AQA treats as content you must use under spec section 3.7.2). OCR's recall list in Section 5d of the H420 spec is longer still. If you've been drilling an OCR revision guide and are sitting Edexcel, you're over-memorising.

The three boards each have their own stats-tests list. All three provide chi-squared, t-test, and Spearman's. OCR also prints the standard-deviation formula and both paired and unpaired t-test formulae on the paper when needed, which is more generous than AQA or Edexcel. See our OCR A-Level Biology data sheet guide for the full OCR list and our AQA A-Level Biology data sheet guide for how AQA structures its provision.

Simpson's index of diversity is used across all three boards but the exact formula provided varies. OCR gives D = 1 - Σ(n/N)²; AQA uses both D = 1 - Σ(n/N)² and d = N(N-1) / Σn(n-1) in different sections of the spec. Edexcel Spec B's Appendix 6 (A.2.3) exemplifies the formula as D = N(N-1) / Σn(n-1), the same form as the AQA content section. The formula is provided in the question stem on Edexcel papers, but it's worth being familiar with that canonical form in advance.

Edexcel also runs two Biology specifications: Spec A (SNAB, 9BN0) and Spec B (9BI0). This guide is Spec B only; if your school teaches SNAB, check your spec code before relying on this list.

The students who pick up marks on Edexcel Spec B calculations work backwards from past-paper questions, not forwards from a formula sheet. Our how to get an A* in A-Level Biology guide walks through the broader revision strategy; the Spec-B-specific calculation habits below sit on top of that foundation.

For magnification, drill the unit conversions. The algebra is trivial once units are right; the mark scheme punishes the wrong unit. 1 mm = 1000 μm, 1 μm = 1000 nm. If an electron micrograph is 42 mm wide at × 10 000 magnification, the real width is 42 mm / 10 000 = 0.0042 mm = 4.2 μm.

For Hardy-Weinberg, practise the two main question types. Given an allele frequency, calculate the proportion of heterozygotes. Given a genotype count, work backwards to allele frequency. Our Hardy-Weinberg equation for A-Level Biology page has the worked examples both ways round.

For stats tests, time yourself on past-paper questions with the formula in front of you. A chi-squared on three or four categories should take three to four minutes once you're fluent. A t-test is longer because of the arithmetic, but still well under ten minutes. Spearman's is the one that drags most students: the rank-assignment step (giving tied values an average rank) catches people out. Drill that specifically.

For standard-deviation interpretation, use real past-paper graphs. Build a mental checklist: what's the mean, what's the spread, do error bars overlap, is the effect convincing? The exam will give you numeric values or error bars; your job is to read them.

For graph-based rate questions, practise extracting a gradient from a tangent to a curve. Edexcel often asks for the rate at a specific time, which means drawing a tangent at that point and finding its gradient. Clear pencil work, two coordinate pairs, divide Δy by Δx. The question will tell you the units.

Cognito's Edexcel A-Level Biology course covers every topic that uses the Spec B formula list, with worked-example videos on magnification, Hardy-Weinberg, chi-squared genetic-ratio tests, Spearman's rank correlation, and index-of-diversity calculations. The maths-skills content runs across the course rather than being siloed into one unit, which mirrors how Edexcel tests it. For broader statistics-interpretation skills (standard deviation, error bars, significance), the course builds those alongside the content they appear in.