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

AQA A-Level Biology (7402) doesn't give you a chunky separate data booklet in the way AQA Chemistry does. There's no downloadable PDF booklet for Biology, so if you've gone looking for one and not found it, that's why. Instead, the formulae and statistical tests you need are set out in the AQA Biology 7402 specification under 'Mathematical requirements and exemplifications' and are typically printed inside the question stems where they're needed.

AQA has a short list of equations it expects you to recall, and a longer list it will provide in the stem. The piece below maps the full list, flags the ones you must memorise, and corrects the standard-deviation misconception that trips up most students in Year 13. For the broader course, see our complete guide to AQA A-Level Biology.

AQA splits its biology formulae into two groups: ones they'll give you in the question stem when needed, and ones you're expected to know cold. The split follows a simple logic. If the formula is long, uses symbols you'd struggle to type under exam pressure, or needs a critical-values table alongside it (every stats test), AQA prints it on the paper. If it's a short biology-specific equation that comes up repeatedly in the course, you're expected to recall it.

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

Magnification is the one you'll use most. Expect it on nearly every Paper 1, usually rearranged to give you the real size when you're told the image size and magnification. The rearrangement is simple algebra, but mark schemes are strict on units: if the image is measured in millimetres, convert to micrometres before dividing (and remember 1 mm = 1000 μm). The magnification formula is set out at spec section 3.2.1.3 of the AQA 7402 specification.

Cardiac output comes up in cardiovascular topics and is the kind of formula students sometimes miss because it's so short. Heart rate × stroke volume = cardiac output. The 2ⁿ formula applies to the number of possible chromosome combinations after independent segregation in meiosis.

NPP = GPP - R shows up in the Year 13 ecosystems topic. Gross primary production minus respiratory losses equals net primary production, measured as biomass accumulated per unit area per unit time. The partner equation for consumers is N = I - (F + R), where I is energy ingested, F is energy lost in faeces and urine and R is respiratory losses: both sit in spec section 3.5.3, so learn them together.

AQA's maths requirement MS 1.9 lists three statistical tests you can be asked to apply: chi-squared, Student's t-test, and a correlation coefficient (the spec doesn't name a specific one; Spearman's rank is commonly used). All three are typically provided with the formula and a critical-values table in the question stem when needed. You pick the right test based on the data type, apply it, and compare your test statistic to the critical value for the correct number of degrees of freedom 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 where you've got predicted phenotype ratios (3:1, 9:3:3:1) and you want to test whether your observed counts are a reasonable match. The t-test is for comparing the means of two samples (effect of a treatment on reaction rate, say). Spearman's is for correlation between two ranked variables, often from an ecology dataset.

Mann-Whitney U is not in the AQA MS 1.9 statistical-tests list. If you see it on a resource for a different board or a university prep course, you don't need it for AQA.

AQA treats standard deviation differently from the other stats concepts. The maths-skills requirements (MS 1.10) say you must be able to understand standard deviation, interpret it, and link it to the spread of a dataset. But the spec is explicit at section 3.4.7: students 'will not be required to calculate standard deviations in written papers'.

That's a useful exemption to know. You should understand what a standard deviation of 2.3 tells you about the spread of your data compared with a standard deviation of 0.5. You should be able to spot when a mean is misleading because the standard deviation is large relative to it. You should be able to use error bars (which usually represent one standard deviation above and below the mean) to judge whether two means are significantly different. But you will NOT be asked to crunch the formula yourself in an exam.

If a question involves standard deviation, it'll give you the value calculated already, usually in a table or on a graph. Your job is to interpret, not calculate.

All three major A-Level Biology boards (AQA, Edexcel, OCR) use the same approach of printing formulae on the paper rather than publishing a separate data booklet. But the exact lists differ, and students who move between past papers across boards can get caught by small details.

AQA's specification (section 3.7.2) states the Hardy-Weinberg equation as p² + 2pq + q² = 1. The companion equation p + q = 1 isn't written out in the spec, but you'll need it in almost every calculation, so learn both.

AQA uses Simpson's Index of Diversity in the form D = 1 - Σ(n/N)² in the maths-skills section (MS 2.3), but d = N(N-1) / Σn(n-1) in the content section (3.4.6). OCR Biology A (H420) uses D = 1 - Σ(n/N)². If you've been drilling with an OCR past paper, be aware the formula might be written differently when it shows up on an AQA paper.

AQA explicitly rules out standard-deviation calculation in written papers (section 3.4.7). OCR Biology prints the standard-deviation formula on the paper itself alongside paired and unpaired t-test formulae. Edexcel Biology Spec B (9BI0) assesses interpretation and can set a calculation with the formula provided.

For mark-release-recapture, the method is named in the AQA spec (section 3.7.4: 'use given data to calculate the size of a population estimated using the mark-release-recapture method'). The spec names the method but gives no formula, so expect the question to supply what you need. On Edexcel Spec B the Lincoln index isn't explicitly surfaced in the specification, which is a cross-board gotcha. See our Edexcel A-Level Biology data sheet guide and OCR A-Level Biology data sheet guide for the per-board detail.

The students who pick up marks on AQA Biology calculations tend to drill the small handful of must-recall formulae to automatic, then focus their revision time on applying the provided ones under time pressure.

For the recall list (magnification, cardiac output, 2ⁿ, NPP = GPP - R, N = I - (F + R), and Hardy-Weinberg's p + q = 1 and p² + 2pq + q² = 1), write them from memory every day for a week during exam season. These are so short that the real revision is building the habit of reaching for them automatically when a question hints at them.

For the provided-in-stem formulae, the revision is about application speed, not memorisation. Work through past-paper questions that use chi-squared, t-tests, Spearman's, Simpson's, and Hardy-Weinberg. Time yourself. If a chi-squared calculation takes you more than 3-4 minutes, you need more reps. The formula is in front of you; the bottleneck is interpretation and arithmetic.

Practice converting units for magnification. 1 mm = 1000 μm, 1 μm = 1000 nm. The magnification formula itself is trivial; it's the unit conversion that trips students up. If an image is 15 mm long and the magnification is × 500, the real size is 15 mm / 500 = 0.03 mm = 30 μm. Mark schemes credit the final answer only if units are correct. The AQA A-Level Biology required practicals guide covers all twelve required practicals, which are assessed through written questions across Papers 1, 2 and 3.

For the standard-deviation exemption, don't waste time learning the formula. Spend that time understanding what standard deviation tells you about a distribution, and practise interpreting error-bar plots. The exam will give you the value; your job is to use it. Our full page on the Hardy-Weinberg equation for A-Level Biology is the standard worked-example reference for the allele-frequency side.

Cognito's AQA A-Level Biology course covers every topic that uses the AQA formula list, with worked-example videos on magnification calculations, Hardy-Weinberg problems, Simpson's and Lincoln index applications, and chi-squared genetic-ratio tests. For the broader statistics-interpretation skills (standard deviation, error bars, significance testing), the maths-skills content runs across the course rather than being siloed into one unit.