Designing Experiments Using the Scientific Method

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Designing Experiments Using theScientific Method
Lesson 1

• Key Terms

Independent Variable
Scientific Method
Hypothesis
Dependent Variable
Control Group
Experiment
Data
Experimental Group
Conclusion
Trial
Procedure
Experimental Error
Variable
Bias
Notice the color of our key terms.
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process
answers
steps
problem
question
organized
educated guess
information
Identify the problem
Form a Hypothesis
Create an Experiment
Perform an Experiment
Analyze the Data
Modify the Experiment
Conclusion
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Lets use some of our key words in an
investigation.
I want to know if warmer temps. cause robin eggs
to hatch faster?

• First, our procedure.

(Step by step plan)
Robins Eggs Experiment





Variable
Control Group
Experimental Group
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4
Number of eggs
Temperature
85 degrees
97 degrees
70
70
Humidity
Lighting
Low Light
Low Light
Variable- Factor that affects results of an
experiment.
There are 2 kinds of variables.
1. Independent Variable-Factor I change to find
out what will happen. Here it is temp.
2. Dependent Variable-Variable affected by
changes in independent variable. Here it is
how long it takes the eggs to hatch.
Control Group-Group used for comparison. All
variables controlled by me.
Experimental Group-Group exposed to changes in
independent variable. Can you see what I changed
in this group?
Every time we repeat this experiment it is called
a Trial.
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Mythbusters using the Scientific Method!
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scientists
observations
experiments
hypotheses
conclusions
results
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Why was my number different than yours!?

• Maybe it was experimental error?

Human Error
True value of measurement vs. Measured value
Sunflower Seed
6 mm
7mm
l___________l
l___________l
Your lab partner measured the same seed at 7mm.
You measured 6mm.
Actual measurement was 6.5 mm. Why?
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But I want my hypothesis to be right!

• This kind of thinking can cause
• bias.

Bias is a wish or expectation that your
experiment will lead to a certain conclusion.
Lets watch a clip to better understand bias.
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Discussion Questions

• 1. What data would lead scientists to accept the
  hypothesis in the experiment with the robins
  eggs? What results might lead them to reject the
  hypothesis? What other variables might affect
  the results?

2. A farmer believes that fertilizer runoff from
a farm is killing the fish in a nearby pond.
The farmer measures the amount of fertilizer in
the pond each week and counts the number of
dead fish. The measurements indicate that, as
the fertilizer concentration increases, the
number of dead fish increases. Can the
farmer confidently conclude that it must be
fertilizer from the farm that is killing the
fish? Why or why not?
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Quiz Time!


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Quiz Time!