“I do not know this experiment, so I do not know what the answer is.” You do not need to know the experiment. You need to read the table for variables, repeats and means.
This page belongs to the SPM Biology help pages. For the skills behind it, see biological investigation.
Why does an unfamiliar experiment feel hard?
Some students look for the experiment in their notes. If it is not there, they think the question cannot be answered. But the table and the method already give you what you need.
Ask three questions: what was changed, what was measured, and what was kept the same.
One example: an invented yeast experiment
An original experiment measured the bubbles of carbon dioxide from yeast in sugar solution at different temperatures. Each temperature was tested three times. The values are invented.
| Temperature (°C) | Trial 1 | Trial 2 | Trial 3 | Mean |
|---|---|---|---|---|
| 20 | 11 | 12 | 13 | 12 |
| 30 | 24 | 26 | 25 | 25 |
| 40 | 40 | 43 | 40 | 41 |
| 50 | 17 | 19 | 18 | 18 |
| 60 | 0 | 0 | 0 | 0 |
Read it in order:
- Manipulated variable: temperature. Responding variable: bubbles per minute.
- Fixed variables: mass of yeast and concentration of sugar solution.
- Mean at 40 °C = (40 + 43 + 40) ÷ 3 = 41.
- Trend: the rate rises to 40 °C, then falls, and is zero at 60 °C.
How do I write a careful conclusion?
State what the data show: “Of the temperatures tested, the highest mean rate was at 40 °C, at 41 bubbles per minute. At 60 °C there were no bubbles, which suggests the yeast enzymes were denatured.”
Then state the limit: “The best temperature may lie between 30 °C and 50 °C, but the data do not show the exact value.” The table supports a range, not a single number.
What can I do on my own?
Use the same three questions on every experiment table. Practise calculating means too, and give the answer to two decimal places when the mean does not come out whole. When you study a worked example, cover its conclusion and write your own first.
If the data come as a graph, use the routine for unfamiliar graphs applies.
When might one-to-one tuition help?
If your conclusions claim more than the table shows, a one-to-one teacher can read them and mark where each one goes too far, so you hear the feedback on your own wording straight away.
This site covers the method for free, and a teacher reviews your answers. See online one-to-one Biology tuition if you would like that.
What to read next
Try the graph evidence and fair-comparison lab for more data to read, and the graph routine for the graph form of the same skill.