Observation vs. Inference
Review - Observation
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What is an observation?
– Using your five senses to take note of and
observe your surroundings
Inference
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An inference is when you make an
assumption or prediction about something
that you observe
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After you make an observation, you usually
make an inference about what is going on
Let’s practice making inferences!
The next three slides show some fossil imprints that
were found during a archeological dig. We’re
going to record some observations and then make
some inferences about what may have happened
millions of years ago….
What do you think happened?
In your notebook, please write a story (around
½ page – be DETAILED please) describing
what you think happened to the creatures in
our fossil evidence
please complete the ‘Inference’ portion of
your worksheet
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P. 4 “Hypothesis, Variables, Constants,
Controls”
Hypothesis
Hypothesis: an educated guess or prediction;
an “if, then” statement
If ____independent variable______
then__dependent variable_______
Example:
Independent Variable:
I feed my cat a lot of food
Dependent Variable
she will get fat
If ___________________________
then _________________________
Remember
Try to use INCREASE and DECREASE in
your hypothesis!
Ex. IF I increase the amount of food I give my cat,
THEN she will increase her weight
Use the following statements and write a good hypothesis – think
about how one thing will affect the other and use your ‘if, then’
statements. Try using the words “increase” and “decrease”
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1) Chocolate may cause pimples.
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2) Salt in soil may affect plant growth.
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3) Bacterial growth may be affected by temperature.
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4) Sunlight may cause skin cancer.
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5) Temperature may cause leaves to change color.
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6) Amount of reading that you do may affect your intelligence.
Types of Variables
There are 2 main types of variables:
Independent Variable: The variable that is changed
by the scientist; the ‘I control’ variable
Dependent Variable: The variable that might change
because of what the scientist changes – what is
being measured
Your hypothesis can TELL you what your
variables are!
Ex. If I drink Mountain Dew before bed, then
I will not sleep very much.
IV: Drinking Mountain Dew
DV: the amount of sleep
Practice
Use this hypothesis to identify the variables:
If I leave all the lights on all day,
then my electric bill will be expensive
IV: ______________________
DV: ______________________
If I brush my cat more, then there will be less
fur on my furniture
IV: ______________________
DV: ______________________
Now read the following experiment and identify
the independent and dependent variables
Elizabeth wanted to test if temperature affected how fast milk
goes bad and curdles. She left milk in a room temperature
closet, a fridge, and a oven that was turned on low heat.
She then measured how rotten the milk was after 10 days.
IV: ____________________________________
DV: ____________________________________
Variable Practice
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Puzzle Example
Students of different ages were given the same jigsaw puzzle to put together. They were timed to see
how long it took to finish the puzzle.
Identify the variables in this investigation:
Independent Variable
Dependent Variable
Electromagnetic Example
An investigation was done with an electromagnetic system made from a battery and wire wrapped
around a nail. Different sizes of nails were used. The number of paper clips the electromagnet could
pick up was measured.
Independent Variable
Dependent Variable
Egg Example
The higher the temperature of water, the faster an egg will boil.
Independent Variable
Dependent Variable
Depth Example
The temperature of water was measured at different depths of a pond.
Independent Variable
Dependent Variable
Constant
Constant: something that scientist makes sure is the
same throughout the experiment
Ex. Watering the plants the same amount of water or
making sure you are testing the same person every
time
Control
Control: The part of the experiment that the
scientist doesn’t change or add the variable
to
Ex. The plant with the white light
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“I want to see if different colors of light help plants grow better. I am
going to take four plants (all the same type) and set them up
underneath different lights. One will be a white light, one will be red,
one will be blue, and one will be green. Everyday, I will water them
the same amount at the same time. I will also record how high each
plant grows for two weeks and then look at my results.”
What is the independent variable?
What is the dependent variable?
What are the constants?
What is the control?
1.
2.
3.
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“I want to see how taping my thumbs will affect my time it takes to
button up a shirt. I will test the same person – they will do three trials
buttoning up the same shirt with their thumbs taped to their palms.
Then I will do three trials where their thumbs are not taped up. I will
average the time in seconds that it takes to button up and shirt with
their thumbs taped and without their thumbs taped.”
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What is the independent Variable?
What is the dependent variable?
What are the constants?
1.
2.
What is the control?
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“I want to see if there if drinking a lot of milk will affect how much you
eat at dinner. I will take 5 people. For three days, I will give them two
glasses of milk to drink before they eat dinner. I will serve the same
food for those three days and they will eat at the same time every day.
After three days of drinking milk, I will then have the people eat for
three days without drinking milk before they eat dinner (again, same
food, same time). I will measure how much food they eat in the three
days that they drink milk and the three days that they don’t drink milk
and compare my results.”
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What is the independent variable?
What is the dependent variable?
What are the constants?
1.
2.
3.
What is the control?