The scientific method

​​In a nutshell

Observations, hypotheses and theories underpin the scientific methods that scientists use. 

Hypothesis

Definition 

A hypothesis is a scientific explanation for an observed event. Although hypotheses may be based on existing scientific knowledge, there is no specific, sufficient evidence for a hypothesis.

Tip: The plural for hypothesis is hypotheses.

Testing a hypothesis

Predictions can be made based on a scientific hypothesis. These predictions can be tested by designing and carrying out scientific experiments. The outcome of the experiment may support or contradict the hypothesis.

Evidence supporting a hypothesis must be peer-reviewed. A peer-review is an unbiased evaluation carried out by other scientists to review the appropriateness of a scientific investigation. Scientists check if:

1. The scientific research is valid.
   
2. The scientific research is original.
3. The scientific research is significant.
   

Valid research is repeatable and reproducible. An investigation is repeatable if the same /similar results are achieved when the scientist repeats the experiment. An investigation is reproducible when another scientist carries out the experiment and also gets the same/similar results.

Accepting or rejecting a hypothesis 

In order for a hypothesis to be accepted, there must be sufficient evidence.

• Logical, specific experiments must be designed
• Multiple scientific experiments need to be carried out
  
• Scientific experiments must be carried out by many different scientists 
• All supporting evidence must be peer-reviewed
  
• Evidence which contradicts the hypothesis must be taken into consideration
  

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Theory  

Definition

A scientific theory is an evidence-based scientific explanation. Theories are based on accepted hypotheses.

Models

A model is a simplified representation of a theory. Scientific theories are complex and sometimes difficult to understand. Scientific models are helpful in understanding theories, since they are simplified representations.

Example

Bohr model of an atom.

The diagram above depicts an aluminium atom based on the Bohr model.