How to Write a Top-Scoring IB Biology Internal Assessment

The Internal Assessment (IA) accounts for 20% of your final IB Biology grade, making it one of the most important components of the course. Here's how to maximize your score.

Understanding the IA Criteria

The IA is marked against five criteria:

Personal Engagement (2 marks) — Show genuine interest and personal significance
Exploration (6 marks) — Background research, methodology, and variables
Analysis (6 marks) — Data processing, presentation, and interpretation
Evaluation (6 marks) — Strengths, weaknesses, and improvements
Communication (4 marks) — Structure, clarity, and academic writing

Choosing Your Topic

The best IA topics are:

Personally interesting to you — examiners can tell when you're passionate
Measurable — you need quantitative data you can analyze statistically
Feasible — achievable with available equipment and time
Focused — one clear independent variable and one dependent variable

Good Topic Examples

Effect of temperature on enzyme activity (catalase in potato)
Effect of light intensity on the rate of photosynthesis (aquatic plants)
Effect of salt concentration on plant cell plasmolysis

Designing Your Experiment

Variables

Clearly identify your independent variable (what you change)
Define your dependent variable (what you measure)
List all controlled variables and explain how you'll control them

Sample Size and Repeats

Minimum of 5 different values for your independent variable
At least 5 trials at each value
Calculate mean values and standard deviation

Data Analysis Tips

Present raw data in clear tables
Use appropriate graphs (scatter plots with best-fit lines, bar charts with error bars)
Include statistical tests (t-test or correlation coefficient) where appropriate
Always include error bars on your graphs
Discuss what your data shows and whether it supports your hypothesis

Common Mistakes to Avoid

Too broad a research question — Be specific and focused
Insufficient data — More trials = more reliable results
Ignoring anomalies — Address outliers in your evaluation
Weak evaluation — Don't just say "human error"; identify specific limitations
Exceeding the page limit — Stay within 6-12 pages

Need expert guidance on your IB Biology IA? Book a session and I'll help you from topic selection to final review.