Making Hypotheses

More than a wild guess

A hypothesis is a sensible prediction that you can check.

A wild guess comes from nowhere, and there is no clear way to check whether it is right.

A hypothesis grows from what you already know or have noticed, and a test can check it.

Scientists use hypotheses to decide what they want to investigate next.

Start with something you notice

Good hypotheses usually start with a small observation.

Maybe you notice that seedlings on a windowsill lean towards the light.

An observation worth predicting about

That noticing gives you something to predict. You are using what you have already seen.

Observations are the seeds of investigations.

Testable means checkable

A hypothesis is testable when an investigation can give you evidence about it.

Here is an example. A plant placed near a window will grow taller than a plant kept in a dark cupboard.

Notice that only the light differs between the two plants, which is why comparing their heights gives useful evidence.

You can then measure both plants and compare their heights.

Those measurements are your evidence.

Making the test fair

A prediction is only useful if your test is fair.

In a fair test you change one thing and keep everything else the same.

Same pot, same soil, same amount of water. Only the light is different.

Then any difference in height has one likely cause.

Ideas you cannot test

Some ideas cannot be tested at all.

"Plants are pretty" is an opinion, so no measurement can settle it.

"Plants like sunshine" sounds scientific, but liking cannot be measured.

"A plant near a window grows taller than one in a dark cupboard" can be tested, because height is measurable.

Wording it clearly

Clear wording makes a hypothesis much easier to test.

Say what you will change, what you will measure, and what you expect to happen.

For example: if I keep one plant near a window, it will grow taller than the plant in the dark cupboard.

Hypotheses can be improved

A hypothesis is rarely finished the first time you write it.

You test it, look at your evidence, and then keep the idea or change it.

A changed hypothesis often leads straight into a new test.

Being wrong is useful

Evidence can support your hypothesis, or it can show that the hypothesis needs changing.

Neither result is a mistake. Both give you real information.

Scientists change hypotheses often. Changing one shows that you have been paying attention to your evidence.

What a strong hypothesis needs

A strong hypothesis does three things at once.

It comes from what you already know, it says what you expect, and it can be checked by a fair test.

In Naturfag tasks, writing it this way shows the examiner how you think.

A hypothesis is a sensible prediction that can be checked by an observation, investigation, or fair test.

• True
• False

Answer: True

This is true. A hypothesis is more than a guess because it can be checked using evidence.

A _____ is a sensible prediction that can be checked. A _____ comes from nowhere and has no clear way to be checked.

Answer: A hypothesis is a sensible prediction that can be checked. A wild guess comes from nowhere and has no clear way to be checked.

A hypothesis uses what you know or have noticed and can be tested. A wild guess has no clear evidence-based starting point or checking method.

A student notices that seedlings on a windowsill lean toward the light. Which is the best hypothesis to investigate?

• Seedlings near a light will lean toward it.
• Seedlings are pretty.
• Plants like everything about sunshine.
• Seedlings will become the biggest plants in the world.

Answer: Seedlings near a light will lean toward it.

The prediction about light direction is based on an observation and can be checked by observing or testing seedlings. The other choices are opinions, vague statements, or unrelated guesses.