Observation and Inference
Name: _________________________ WS#
Date: _________________
Color: _______________
What do you need in order to form a hypothesis? A hypothesis is not just
a random guess; it is a prediction bases on some facts, or observations. But a
hypothesis is not a proven fact, so it is also based on inference. Inference means
drawing conclusions about the things you have observed.
For example, suppose you hear a crash coming from your bedroom. You
enter the room to find your window broken and a baseball rolling across the floor. You can
infer that someone hit the baseball through your window and broke it. You did not see the
incident happen, but you can make a hypothesis based on your inference.
A very important part of scientific thinking—and thinking in general—is the ability to
separate observation and inference. Observations are things you have experienced through the
senses, by seeing, hearing, tasting, touching, or smelling. An inference is an explanation or
interpretation of what you have observed.
Two people can observe the same situation, and if they are careful observers, they can
use their observations to come up with facts about the situation that are not subject to opinion.
Inference is very different. Inference depends greatly on personal opinion and ideas.
Therefore, two people might observe the exact same events, and infer very different things
from them. Hypothesis must be tested. For this reason they are not considered to be fact. If
hypotheses were based only on observation and not on inference, there would be no need to
test them; they would be fact.
Practice: Read the following passage and decide: (a) what observations Inspector Richards made
and (b) what inferences were based on each observation.
Murder?
The rain had just stopped. Inspector Richards arrived at the house at 2
p.m. The front door was locked. He pried open the door and went in. Mrs.
Williams was lying in bed. She was dead. The bedroom window faced the
garden. The window was open and there were several small puddles of water
between Mrs. Williams’s bed and the window. The woman was wearing a pearl
necklace, and there was a bottle of pills on the night table near the bed. Mr.
Williams was out of town on business.
Because Mrs. Williams was still wearing her pearls, robbery could not
have been the motive. It was obviously a case of murder. The murderer must
have come in through the bedroom window and killed Mrs. Williams. The
puddles of water were probably left by his shoes.
a. Observations:
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2. ___________________________________________________________________________
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3. ___________________________________________________________________________
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4. ___________________________________________________________________________
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b. Inference:
a. ___________________________________________________________________________
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b. ___________________________________________________________________________
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c. ___________________________________________________________________________
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d. ___________________________________________________________________________
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What is a HYPOTHESIS?
A hypothesis is a possible explanation of why something may have
happened or a prediction of what might happen. It is an explanation of the
possible cause of a problem or a possible solution to a problem.
For example, imagine that you are sitting at home when suddenly the lights
go out. You need to find out why the lights went out, so that you know what to do to get the
lights back on. In coming up with possible causes, you are formulating hypotheses. Some of
your hypotheses might include the following: a problem with the electric generator at the
power station, a break in the electric cable leading to the house, or a circuit overload caused by
someone using too many kitchen appliances at one time. Each of these hypotheses can be
tested to determine if it is the true cause of why the lights went out.
In order for a predicted solution to be a hypothesis, you must be able to test it.
Otherwise, your prediction or solution is merely a guess. The hypothesis is the most important
tool of scientific research. Most scientific experiments begin with a hypothesis. Then the
experiment or experiments are carried out to test the hypothesis.
When writing a hypothesis, use these words:
If….…then………..as compared to……..
Before a scientist formulates a hypothesis, a scientists put a lot of effort into
gathering observations before making their hypothesis. It is also correct to say that a
scientist states, forms, or frames a hypothesis. The hypothesis is tested by observation and
experimentation. After the scientist weighs the evidence, the hypothesis is accepted (proved,
verified, or confirmed) or rejected (disproved).
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Practice: For each situation formulate a hypothesis using the correct format. Then explain how
you would test your hypothesis. Make sure you answer both parts.
1. You order an item by mail. It was supposed to arrive in 2 weeks, but 3 weeks later the
package has not arrived. Why?
Hypothesis: ______________________________________________________________
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How to test hypothesis: _____________________________________________
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2. You are supposed to meet a friend for lunch at 1:00pm. Your friend has never been to the
restaurant, so you wrote out directions for him. By 2:00pm he has not arrived. Why?
Hypothesis: ______________________________________________________________
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How to test hypothesis: _____________________________________________
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3. You are trying to grow a plant in your bedroom. The plant looks healthy at first, but in a few
days, the leaves turn brown, and the plant appears to die. What happened?
Hypothesis: ______________________________________________________________
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How to test hypothesis: _____________________________________________
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