Data and investigations is the part of IGCSE Biology where you stop recalling and start judging an experiment: is it fair, is the evidence strong enough, and how could it be improved? The marks come from precise wording, not from extra facts.
The skills here appear in written papers with a supplied method or table, and they support any practical work your school arranges. Check the current Cambridge IGCSE Biology 0610 syllabus page, linked from the Biology learning guide, for how your exam year assesses them.
What should I already know?
You need to recognise the independent variable (what you change), the dependent variable (what you measure) and the control variables (what you keep the same). You also need to calculate a mean and a range, and to read values from a table.
Plotting points on a grid is assumed from maths. If you can already do those things, you are ready to start.
An orienting example
All data here are invented for practice. A student tests whether a fertiliser solution increases the height of bean seedlings. After 14 days the fertiliser seedlings measure 12, 15 and 21 cm, and the water-only seedlings measure 13, 14 and 15 cm.
The fertiliser mean is (12 + 15 + 21) ÷ 3 = 16 cm and the water mean is (13 + 14 + 15) ÷ 3 = 14 cm. It looks like a 2 cm gain.
Now examine the evidence. The water-only set is the control, but there are only three seedlings per set, and one tall seedling (21 cm) drives the whole difference: without it, the fertiliser mean is (12 + 15) ÷ 2 = 13.5 cm, lower than the control. The honest conclusion is that this sample is too small to decide, and a better method uses, for example, 20 seedlings per set.
That short paragraph used three skills from this module: a control, a sample-size limitation and a specific improvement.
In what order should I study the lessons?
- Choose a control for a supplied experiment: start here because every later skill assumes you can see what the comparison is.
- Identify a sample-size limitation: it shows why one small comparison is not enough on its own.
- Draw an interpretable graph with units: this turns a results table into evidence you can read.
- Distinguish repeatability from validity: two words students swap, with a clear test for each.
- Turn a vague improvement into a specific measurement change: the final step, where you write the answer a mark scheme rewards.
Sample-size thinking also supports cell division and inheritance, where a small number of offspring rarely matches a model ratio exactly.
Which traps catch students most?
- Writing “it was not a fair test” without naming which variable was not controlled.
- Saying “do it more times” when the question wants a number, what is repeated and what is calculated from it.
- Drawing a graph without units on the axes, or joining points dot to dot when a smooth trend is expected.
- Using repeatable and valid as if they meant the same thing.
- Suggesting “use more accurate equipment” without naming the instrument and what it measures.
How should I use the practice set?
Finish at least two lessons, then try the mixed practice for this module. Write each answer in full sentences before opening the working, and note which lesson any slip belongs to. The mistake log and retest queue is a simple way to track that.
The inheritance model board also shows how a small sample can differ from the expected ratio. If these questions keep losing marks for wording, online one-to-one Biology tuition can focus on that with your own answers.