What is a Hypothesis ?
Which question is the best question ??
Testable Questions
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Can be answered through hands-on investigations.
They are NOT opinion questions or questions that can
be answered by doing research in a book or on the
internet.
You must be able to measure the results in some way
for it to be considered a testable question.
3 types of testable questions
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1. The effect question
⚫ What is the effect of sunlight on the growth of plants?
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2. The how does affect question
⚫ How does the color of light affect the growth of plants?
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3. The Which/What and verb question
⚫ Which/what paper towel is most absorbent?
Let’s practice identifying testable
questions…
❑
What types of apples grow in Michigan?
❑ Not a testable question. It can not be tested through
an experiment. You can answer this question with
research on the internet or in a book.
❑
How does talking to a plant affect a
plants height?
✓ Testable question. It is a How Does
Affect question.
❑
Which pill design- tablet, caplet, or capsulewill dissolve faster?
✓ Testable question. It is a Which/What verb
question.
❑
Which planet is the most interesting one
to study?
✓ Not a testable question. It is an opinion and
can not be proved in an experiment.
❑
How does stirring affect the rate that salt
dissolves in water?
✓ This is a testable question. It is a How Does affect
question.
What is a Hypothesis?
How does a hypothesis begin?
What do you do with it?
How do you make one?
Writing a Hypothesis
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A hypothesis is a special kind of prediction that forecasts
(predicts) how changing one part of an experiment will
affect the results.
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It is NOT a guess. It is an informed and well-thought out
prediction that requires background information.
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You can also think of it as a cause-effect statement.
How does a hypothesis begin?
A scientist bases his/her hypothesis both on what he
or she has observed, and on what he or she already
knows to be true.
Making a hypothesis is a step in the
Scientific Method
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2.
3.
4.
5.
6.
7.
The 7 basic steps of the scientific method:
Asking a question
Completing research
Making a hypothesis
Planning an investigation
Recording and analyzing data
Explaining the data
Communicating the results
What do you do with a hypothesis?
The hypothesis that a scientist creates leads him or her
to make a prediction that can be tested next in an
investigation.
What do you do with a hypothesis?
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Notice how the example scientist’s hypothesis makes
a prediction that can be tested:
“If I water the tomatoes in my garden daily then they
will grow faster because tomatoes grow more when
they get more water.”
What will the scientist do in the investigation to test
her hypothesis?
A hypothesis is not just a prediction
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In science a prediction is an educated guess about the
expected outcome of a specific test
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In science a hypothesis goes further
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A hypothesis includes a possible explanation about
why the expected outcome of a test will occur
Prediction vs. hypothesis
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Example Prediction: If it gets cold outside the leaves
will change colors.
Example Hypothesis: If it gets cold outside then the
leaves will change color because leaf color change is
related to temperature.
How do you write a hypothesis?
A good hypothesis includes two parts:
1. a prediction about the outcome of a
scientific investigation
----and---2. an explanation for why those results
will occur
How do you write a hypothesis?
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A hypothesis is worded as a prediction about what will
happen if you change something
Example: If students eat a lot of candy then they will
get more cavities because sugar on teeth causes
cavities.
How do you write a hypothesis?
A good hypothesis is worded like this:
If…..then…...because…….
OR
I predict…because
I think…because
Hypothesis example
If students eat a lot of chocolate then they will get a
sick stomach because a lot of chocolate all at once is
hard for the stomach to digest.
If….then….because….
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After the word “If”… explain what will change in the
investigation
After the word “then” …write what you predict will
happen as a result of that change
After the word “because” …explain why you think the
result will happen
Another hypotheses
If salt is added to a plant’s soil then the plant will die
because salt will dry out the soil so that there is not
enough water left for the plant.
Another Hypothesis
If people spend more time in the sun then they will be
more likely to get skin cancer because exposure to
ultraviolet light in sunlight causes skin cancer.
Variables
Variables
Variables are conditions that could affect the
outcome of an experiment.
Think about all of the different things that might
affect how well a student does on a test.
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-- their amount of sleep
– how long they studied
–if they’re feeling well
– how well they paid attention in class
All of those things are variables- they affect how
well the student will perform.
There are 3 types of variables.
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The independent variable is what you change on purpose
in an experiment. Usually there is only one independent variable
in an experiment. Ask yourself “What did I change?”
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The dependent variable is what you measure in an
experiment. Ask yourself “What do I observe?”
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The controlled variable is the condition that remains the
same in an experiment. Ask yourself “What did I keep the
same?”
Q: How does the size of the faucet opening affect the
amount of water that flows out of it?
Independent
Variable
(What I change)
Dependent
Controlled
Variable
Variable
(What I observe) (What I keep
the same)
Water faucet opening The amount of water The faucet
(closed, half open,
flowing, measured in
fully open)
cups per minute
Q: How does the temperature of water affect
the rate that sugar dissolves?
Independent
Variable
(What I change)
The temperature of
the water in degrees
Fahrenheit.
Dependent
Controlled
Variable
Variable
(What I observe) (What I keep
the same)
The amount of sugar Stirring and
that dissolves
the type of
measured in grams. sugar.