IB Biology IA Criteria (2026)

What Is the Biology IA and Why Do the Criteria Matter?

The IB Biology Internal Assessment is a 3,000-word investigation where you design and carry out your own experiment - and it’s worth 20–25% of your final grade, depending on whether you’re SL or HL.

You choose the question, plan the method, analyze the data, and explain what it all means. But to get a top mark, it’s not enough to just do an interesting experiment - you have to meet the four assessment criteria the IB uses to grade every Biology IA.

This page explains each IB Bio IA assessment criteria one by one, so you know exactly what examiners are looking for.

Overview: IB Biology IA Marking Criteria

Your Biology IA is marked out of 24 points, split evenly across four criteria:

IB Biology IA Criteria Table

Each criterion is worth up to 6 marks, and the rubric is the same for both SL and HL students - what changes is usually the depth or complexity of the topic, not the expectations.

IB Biology Criterion A: Research Design

What does a strong Biology IA design look like?

This first criterion is all about how well you plan your investigation - from your research question to your method and everything in between.

A strong design shows that you understand the science, have thought it through, and can explain why you did what you did.

What examiners look for:

• A focused, testable research question
• Relevant background theory to show scientific understanding
• A clear hypothesis (optional, but often expected in Biology IAs)
• Well-defined independent, dependent, and controlled variables
• A replicable method with controls in place
• Justification of choices - why you chose your method, range, or materials
• Any safety, ethical, or environmental considerations, if relevant

Strong vs weak examples:

Strong vs Weak IA Design

IB Biology Criterion B: Data Analysis

What makes a strong data analysis in the Biology IA?

This criterion is about how well you process, interpret, and present your results. Aside from collecting data, it’s important to show that you understand what your results mean, and how they connect to your research question.

What examiners look for:

• Accurate, relevant data - enough trials and a meaningful range
• Sample calculations shown clearly, using correct significant figures
• Graphs with correct labels, units, titles, error bars, and trendlines
• Discussion of patterns and anomalies in your results
• Clear explanation of uncertainties and limitations
• Analysis that clearly connects to your variables and biological concepts

Common issues to avoid:

• Inconsistent or unlabeled data tables
• Missing units or error bars
• Only describing results, without interpretation
• Ignoring anomalies or uncertainty

Good data analysis makes it easy for the examiner to see what you found - and how well you understand it.

IB Biology Criterion C: Conclusion

How do you write a strong conclusion in your Biology IA?

Your conclusion should directly answer your research question - using your data and scientific understanding, not just subjective reflection.

What examiners look for:

• A clear, specific answer to your research question
• Justification based on key data trends or averages
• Connection to biological theory or literature
• Acknowledgement of limitations that affect reliability
• A sense of how confident you are in your findings

This section doesn’t need to be long, but it does need to show that you understand what your results mean - and how they fit into the bigger picture.

IB Biology Criterion D: Evaluation

What makes a strong evaluation in your Biology IA?

This section is about reflecting critically on your investigation - what went well, what didn’t, and how it could be improved in a realistic and scientifically sound way.

What examiners look for:

• Strengths and weaknesses of your design and execution
• Specific sources of error - both random and systematic
• The impact of those limitations on your data and conclusions
• Realistic improvements that address the weaknesses directly
• (Optional but encouraged): a clear, relevant extension or follow-up experiment

Common mistake:

• Vague or generic reflections like “human error” or “use better equipment” - without detail or context

Your evaluation is one of the best places to show that you understand the scientific process - and how you’d improve if you did it again.

Final Checklist: Use the Criteria to Review Your Bio IA

Before you submit your Biology IA, run through this quick check based on the four criteria:

• Is my research question testable - and is my method clearly explained and justified?
• Is my data processed clearly, with uncertainties and interpretation?
• Does my conclusion answer the research question using evidence and relevant biology?
• Did I evaluate the strengths and weaknesses honestly - and suggest realistic improvements?

Need Help With Your Biology IA?

Whether you’re still shaping your research question or polishing your final evaluation, you don’t have to figure it all out alone.

Our IB Biology tutors have done the IB themselves and helped thousands of students submit stronger IAs - with clarity, confidence, and higher marks to show for it.

Get expert, 1-on-1 support for any part of the process:

• Planning your experiment
• Structuring your report
• Strengthening your analysis, conclusion, or evaluation