A step-by-step writing frame for the IBDP Biology Internal Assessment. Each section pairs a place to write with the rubric, worked examples, and the traps that cost students marks — built around hypotheses, standard deviation and statistical testing.
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This writing frame walks you through every part of the IB Biology Internal Assessment: a focused, manipulable research question; a referenced biological background; an explicit null hypothesis (H₀) and directional alternative hypothesis (H₁) tested at α = 0.05; the independent, dependent and a sufficient range of controlled variables for a living system; sampling and standardisation with enough replicates per group; processing your replicates into mean ± standard deviation and standard error; an appropriate statistical test (a t-test for two groups, a one-way ANOVA for three or more) with a clear decision at p < 0.05; a graph of group means with SD error bars; and a conclusion weighed against the biology and referenced secondary data. Free to start; exports to DOCX and PDF.
The IA is assessed against four equally weighted criteria — Research design, Data analysis, Conclusion and Evaluation, six marks each for 24 in total. Examiners reward a methodology matched to a biologically grounded question, data recorded and processed with a measure of variability (standard deviation or standard error), an appropriate significance test correctly interpreted, a conclusion justified against accepted theory and secondary data, and an evaluation that distinguishes biological variability from systematic error.
Report each group as mean ± standard deviation, calculated with the sample formula s = √[Σ(x − x̄)²/(n − 1)], and use the standard error (SE = SD/√n) for tighter error bars where appropriate. Choose a t-test, one-way ANOVA (with a Tukey HSD post-hoc test) or Pearson correlation to match your hypothesis, then reject H₀ only when p < 0.05 — and read whether your SD error bars overlap.
The full Research Design section is free to use — start writing straight away, no payment required. Sign in to save your draft and sync it across devices. Every section, worked example and rubric note is written by experienced IB Biology examiners.
A strong question is focused, manipulable and biologically grounded. Name the organism or biological system, the independent variable with its range and units, and the dependent variable with how it is measured — for example, "How does the concentration of sodium chloride (0.0–2.0% w/v) affect the mean root length (mm) of mung bean seedlings after 10 days?" It needs a measurable, repeatable biological response and enough replicate data to support a statistical test.
Match the test to your data and hypothesis: a t-test to compare two group means, a one-way ANOVA (followed by a Tukey HSD post-hoc test) for three or more groups, and a Pearson correlation for the strength of a linear relationship between two continuous variables. State the null hypothesis, test at α = 0.05, report the test statistic and p-value, and reject H₀ only when p < 0.05.
Aim for at least five replicates per level of the independent variable so that a mean and standard deviation are meaningful; many strong IAs use ten or more. Living things vary, so more replicates tighten your standard error and error bars and increase the power of your statistical test to detect a real effect. Standardise your organisms (age, size, source) and allocate them randomly to reduce bias.
Yes — the full Research Design section is free to use, and you can sign in to save your work and sync it across devices. When you are ready, your IA exports to both DOCX (Word) and PDF, formatted in third person and past tense with your references in APA, MLA or Harvard style.