The IB Biology Internal Assessment (IA) is more than just an experiment—it’s an exercise in scientific thinking, research, and communication. To find out what separates a high-scoring IA from a forgettable one, we spoke to a seasoned Biology IA tutor who has supported dozens of students through the process. Here’s what we learned.

Understand the Rubrics—Deeply

Before anything else, take the time to understand the rubrics. Many students jump into designing their experiment or choosing a research question without knowing what they’re actually being graded on. The rubric highlights key assessment criteria: clarity of the research question, justification of methodology, depth of analysis, personal engagement, and more. Knowing this early helps ensure your time and effort are focused where they’ll count.

Let Feasibility Guide Your Research Question

A common pitfall is choosing a flashy or interesting research question without considering whether it can actually be carried out. Before locking anything in, think through the methodology:

• Are the required materials and chemicals available in your school lab? 
• Do you need specialised equipment (like a spectrophotometer or incubator)? 
• Has a similar method been used successfully in other studies? 

It’s smart to look up research papers that use comparable techniques or even ask tools like ChatGPT to help brainstorm testable ideas. Your research question should emerge after confirming the experiment is viable, not the other way around.

Demonstrate Relevance and Engagement

Examiners are looking for biological significance and personal engagement. Your IA should show why the experiment matters in a broader biological context. For example, studying how pH affects soy milk protein coagulation could tie into food science, agricultural practices, or nutritional research. If it’s a topic you’re personally invested in—say you drink soy milk daily—that connection helps demonstrate your engagement, which is part of the rubric too.

Structure for Clarity and Logic

Good science is readable science. A strong IA is easy to follow from start to finish, even for someone unfamiliar with the topic. Organise your work in a logical flow: from background and RQ to methodology, data, and analysis. Have a friend or classmate (preferably someone not doing Biology) read it—if they understand it, that’s a strong sign your writing is clear.

Back Everything Up with Research

Strong IAs are grounded in real science. Claims and decisions should be supported by credible sources—don’t just say “apple juice is acidic,” show it using data or literature. A rigorous literature review strengthens your rationale and adds weight to your conclusions. Find papers that are similar (but not identical) to your investigation. This also helps ensure your research question is scientifically valid and not too simplistic.

Mistakes to Watch Out For

Certain errors show up again and again:

• Unjustified methods: Every step in your method should be explained. Why that temperature? Why that time interval? Justifications are often weighted heavily in the marking scheme. 
• Weak control of variables: Go beyond listing controlled variables. Explain how and why you controlled them. For example, “Room temperature was maintained using air-conditioning to avoid enzyme denaturation due to heat fluctuations.” 
• Poor statistical analysis: Choosing the wrong statistical test—or failing to explain why a test was used—can undermine your analysis. You’ll commonly need a two-tailed t-test, ANOVA, or Tukey test. Don’t just include the numbers; explain what they show and why it matters. 
• Lack of supporting evidence: Vague statements don’t hold up. Instead of writing “apples are sweet”, cite research quantifying their sugar content, or include your own measured Brix values.

Start Early

Students often underestimate how long it takes to run trials, revise their IA, or deal with unexpected issues. Start early so you have time to refine your experiment, repeat tests if needed, and incorporate feedback. Make sure you also schedule your lab time well in advance.

Final Thoughts

Writing a top-tier Biology IA is about more than running an experiment—it’s about designing thoughtful research, making informed decisions, and communicating your findings clearly. Ground your work in evidence, think critically about every step, and keep the rubric close by as your guide.

If you’d like support in your Biology IA, do reach out to us, we’re here to help!