IB Internal Assessment: A Practical Guide

Step-by-step guidance for planning, writing, and excelling in your IB Internal Assessment.

What Is an Internal Assessment?

An Internal Assessment (IA) is a substantial piece of coursework that every IB Diploma Programme student must complete in each of their six subjects. Unlike the external examinations held in May, which are written and graded entirely by the IB, Internal Assessments are completed during the course under the guidance of the classroom teacher and then submitted to the IB for external moderation, which ensures consistency of grading across schools worldwide. The weight of the IA in the final subject grade varies by subject but typically ranges from 20 to 25 percent, making it a significant component that can meaningfully raise or lower a student's overall score. In the sciences (Physics, Chemistry, Biology), the IA takes the form of an independent laboratory investigation where students design their own experiment, collect and analyse data, and evaluate their methodology and results. In Mathematics, the IA is the Mathematical Exploration, a written investigation into a topic of the student's choice. In English Literature and Language, students complete written commentaries or comparative essays. In History, the IA is a historical investigation based on primary and secondary sources. The subjects where IAs carry the most weight and demand the most independent work are arguably the sciences and mathematics, where the combination of experimental or exploratory work with rigorous analysis and evaluation creates a task that is substantially more complex than a standard essay or examination. Understanding the nature and expectations of the IA from the very beginning of the DP is essential, as early planning and steady progress are far more effective than last-minute efforts.

Choosing Your Topic

The choice of topic is arguably the single most important decision in the entire IA process, and it is one that students frequently get wrong. The most common mistake is choosing a topic that sounds impressive but is too broad, too complex, or too disconnected from the student's genuine interests to sustain a focused and personal investigation. The best IA topics share several characteristics. First, they arise from genuine curiosity: a student who is passionate about cooking might investigate the effect of temperature on the rate of enzymatic browning in apples, while a student interested in sports might analyse the biomechanics of a tennis serve using physics principles. Second, the best topics are feasible: the student must be able to collect reliable data within the time and resource constraints available. An experiment that requires expensive laboratory equipment not available at school, or a mathematical investigation that depends on data sets the student cannot access, will quickly lead to frustration and poor results. Third, the topic should allow the student to demonstrate the full range of skills assessed by the IB criteria, including personal engagement, clear methodology, mathematical or scientific analysis, and critical evaluation. Before committing to a topic, students should discuss their ideas with their subject teacher, review the assessment criteria carefully, and look at exemplar IAs that have received high marks to understand what examiners value. Starting this process early, ideally in the first term of the DP, gives students time to refine their research question and conduct preliminary tests before the formal IA timeline begins.

Choose a topic you are genuinely curious about: personal engagement is a formal assessment criterion, and examiners can tell when it is authentic.

Make sure you can collect reliable data with the equipment and time available to you: feasibility is as important as ambition.

Check with your teacher early and often: they cannot write the IA for you, but they can steer you away from common pitfalls.

Look at exemplar IAs that scored well to understand the standard expected: the IB publishes sample work with examiner comments.

Structure and Writing

A well-structured IA follows a clear logical progression that mirrors the scientific method or, in the case of mathematics, a coherent investigative narrative. The standard structure for a science IA includes an introduction with a focused research question and relevant background theory, a methodology section that describes the experimental design in sufficient detail for replication, a data collection section with raw data presented in clear tables, a data analysis section with processed data and appropriate use of statistical tools or graphical representations, and an evaluation section that discusses strengths, limitations, and suggestions for improvement. For a mathematics IA, the structure is less rigid but should include an introduction establishing the research question and personal rationale, a development section where mathematical tools are applied systematically, and a conclusion with reflection. Word limits vary by subject: science IAs have a recommended length of 6 to 12 pages, while mathematics IAs should be 12 to 20 pages. Exceeding these limits does not automatically result in a penalty, but examiners view excessive length as a sign of poor focus and editing. What examiners look for above all else is evidence of personal engagement, which means the student's own voice, choices, and thinking should be visible throughout, not just in a brief personal reflection at the end. The analysis must go beyond basic description to show genuine interpretation and critical evaluation of results. Students who can honestly discuss what went wrong, why their results may be uncertain, and what they would do differently demonstrate the intellectual maturity that earns the highest marks.

Common Mistakes to Avoid

Having worked with hundreds of IB students on their Internal Assessments, several recurring mistakes stand out as the most damaging to grades. The first and most frequent is overcomplicating the topic. Students often believe that a more complex research question will impress examiners, but the opposite is usually true. A simple, well-executed investigation with thorough analysis and honest evaluation will score higher than an ambitious project that the student cannot fully control or understand. The second common mistake is poor data analysis. In science IAs, students sometimes present their data without calculating uncertainties, drawing error bars, or performing appropriate statistical tests. In mathematics IAs, students may apply advanced techniques they found online without demonstrating genuine understanding of how and why those techniques work. Examiners are not impressed by complexity for its own sake; they want to see that the student can justify every analytical choice they make. The third major error is neglecting the evaluation and reflection sections. Many students treat these as afterthoughts, writing a brief paragraph about "human error" without engaging critically with the specific limitations of their own work. The evaluation should identify concrete weaknesses in the methodology, explain how these affected the results, and propose specific, realistic improvements. Similarly, reflection should demonstrate that the student has learned something meaningful from the process, not just that they enjoyed it. Finally, leaving the IA to the last minute is a mistake that compounds all the others. The IA is a substantial piece of work that requires multiple drafts, teacher feedback, and revision. Students who begin early have the luxury of time to refine their work, while those who procrastinate often submit rushed, underdeveloped investigations that fail to reflect their true ability.

Your IA topic does not need to be groundbreaking -- examiners value clear methodology, honest analysis, and genuine personal engagement over complexity. A well-executed simple investigation will always outscore a poorly executed ambitious one.