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Thinking Scientifically
Thinking Scientifically Revision
Thinking Scientifically
It is vital that when we finish our experiments, we analyse the results scientifically. We must make a valid conclusion, and evaluate the experiment as a whole.
Making Conclusions
To make a conclusion, we should follow these steps:
- Determine if your results are valid.
- Determine if there is a pattern or relationship in your results.
- Write a conclusion that describes this pattern and relates it back to your original hypothesis. Quote your results as evidence for your conclusion.
- Ensure that your conclusion only considers the data you have, and doesn’t conclude anything further than what your data shows.
Correlation and Causation
“Correlation does not mean causation.”
This means that just because there is a correlation in your results, it doesn’t necessarily mean that the independent variable you are changing causes this relationship.
For example, someone might find that there is a relationship between how much hair a man has and his life span. But this does not necessarily mean that having less hair causes men to die earlier.
There could be other reasons that there is a relationship. There might be other variables at play. For example, men often lose their hair due to stress, so it could be the stress that causes their shorter lifespan and not the hair loss.
It could just be coincidence that two variables appear to show a correlation. You might find that someone else investigates your hypothesis and finds completely different results.
Evaluation
Once you’ve completed your investigation and have a conclusion, a good practice is to evaluate your investigation as a whole.
- Discuss how valid your method was, and whether you controlled all control variables and only changed the independent variable.
- Discuss if your results were repeatable and reproducible. Also discuss if they were accurate and precise.
- Discuss any anomalous results, and try to explain possible reasons for them. Comment on any possible errors that may be the cause, and relate this to your uncertainties.
- Suggest any changes or improvements you would make if you were to do the experiment again. Also discuss any further work that could be done.
Thinking Scientifically Example Questions
Question 1: A student makes a conclusion based on the following set of results from a Hooke’s Law investigation.
| Mass \left(\text{kg}\right) | Force \left(\text{N}\right) |
| 1 | 1.70 |
| 2 | 3.29 |
| 3 | 5.07 |
| 4 | 6.68 |
“As the mass on the spring increases, force will always increase.”
Determine what is wrong with their conclusion.
[2 marks]
The experiment only tests masses up to \boldsymbol{4 }\: \textbf{kg}. We can’t comment on what will happen with more mass than this. The spring may break.
Question 2: Give one reason why two variables may appear to have a relationship when in reality they are unrelated.
[1 mark]
Any one from:
- There might be other variables causing the relationship.
- It might just be a coincidence.
Question 3: Explain how a student could evaluate their investigation.
[3 marks]
Any 3 from:
- Discuss how valid their results are.
- Discuss if the results are reproducible and repeatable.
- Discuss if the results are accurate and precise.
- Discuss anomalous results.
- Suggest improvements.
