Aim & Hypothesis

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What is an Aim?

In the scientific method, the AIM is a statement that describes the purpose or objective of an investigation. It clearly states what you are trying to find out or achieve through the investigation.

The Aim should:

Be easy to understand and avoid unnecessary words.
Be specific and focused.
Not make a prediction about the outcome (because thats a hypothesis!)

For example,

Instead of: "To find out if plants grow taller in sunlight." (This is a hypothesis)
A better aim would be: "To investigate the effect of sunlight on plant growth."

What is a Hypothesis?

Before starting an experiment, scientists write a HYPOTHESIS. A hypothesis is an educated guess (based on evidence and prior knowledge to answer the question behind the experiment (the research question).

Observation investigations are a starting point, leading to futher investigations. A new hypothesis is made, based on observational evidence and inferences from these initial observations. This new hypothesis then leads to follow up experiments.

Writing a Hypothesis

In all types of investigations, the hypothesis is always written after the AIM (purpose) and before the METHOD (procedure). However, the wording of the hypothesis will change depending on the type of investigation.

Observation Investigations

In observation invesgitations (where the goal is to understand things in their natural setting), a hypothesis is written as:

I think that...

Fair Test Investigations

In fair test investigations (where the goal is to determine how changes in one factor affect another), a hypothesis is written after the aim (purpose) and before the method (procedure). The hypothesis must be worded in such a way that it can be tested in an experiment. To write a hypothesis, you will need to identify the dependent and independent variables.

The independent variable is the variable that you, the 'scientist', control or set - what you do.
The dependent variable is the variable that changes depending on what you do. The results of the dependent variable are what you observe or measure.

A good hypothesis should be written in terms of the dependent and independent variables. It should be written like this:

If (I do / change this - independent variable) then (this - dependent variable) will happen.

An example of a hypothesis is:

If I bake potatoes, pumpkin and sweet potatoes at the same temperature, the the pumpkin will cook the fastest.

The 'if' part of the hypothesis is what you believe to be true. The 'then' part is what you will observe if the 'if' part is, indeed true. A correctly written hypothesis will tell you exactly how to conduct the experiment.

A Valid Experiment

A true or valid experiment will test only one hypothesis at a time. If you get this far and realise your question cannot be answered by investigating, you will need to go back and look at whether any part of your question involves something that cannot be measured. If so, rephrase your question so it can be measured.

Writing a hypothesis from an inference

Another way to write a hypothesis is to make an inference and then convert that inference to a hypothesis. For example, many parts of New Zealand have a dry season. Grass changes from being green to being brown or yellow. One observation is that the grass does not turn brown as quickly near the edges of a concrete path but remains green for much longer.

We can make an inference, based on our experience and deduced from the facts. An inference is like an educated guess and is a possible answer. A valid inference is one that explains all the observations.

Some inferences that may explain why grass growing near the edge of the concrete path remains green in summer are as follows.

This grass receives the rain runoff from the path when it rains.
The concrete path insulates the grass roots from the heat and cold.
People do not walk on this part of the grass.
The soil under the path remains moist while the soil under the open grass dries out.
More earthworms live under the path than under the open grass.

For Inference 2 above, the hypothesis might be:

If the temperature of the grass roots were measured, then the grass roots under the path would be cooler than the grass roots beside the path.

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