Scientific Method

Steps in the Scientific Method
Observation
Hypothesis
Experiment
Data Collection
Conclusion
Retest

Observations
Gathered through your senses
A scientist notices something in their natural world

Observations
An example of an observation might be noticing that many salamanders near a pond have curved, not straight, tails

Hypothesis
A suggested solution to the problem.
Must be testable
Sometimes written as If…Then… statements
Predicts an outcome

Hypothesis
An example of a hypothesis might be that the salamanders have curved tails due to a pollutant in the moist soil where they live.

Experiment
A procedure to test the hypothesis.

Experiment
Variable – factor in the experiment that is being tested

Experiment
A good or “valid” experiment will only have ONE variable!

Controls and Variables

Scientific Experiments Follow Rules
An experimenter changes one factor and observes or measures what happens.

The Control Variable
The experimenter makes a special effort to keep other factors constant so that they will not effect the outcome.
Those factors are called control variables.

What is the Purpose of a Control?
Controls are NOT being tested
Controls are used for COMPARISON

Other Variables
The factor that is changed is known as the independent variable.
The factor that is measured or observed is called the dependent variable.

Example of Controls & Variables
For example, suppose you want to figure out the fastest route to walk home from school.
You will try several different routes and time how long it takes you to get home by each one.
Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.

What are the Variables in Your Experiment?
Varying the route is the independent variable
The time it takes is the dependent variable
Keeping the same walker throughout makes the walker a control variable.

One more thing… it is best to make several trials with each independent variable.

Valid Experiments

Remember: To be a Valid Experiment:
Two groups are required --- the control & experimental groups
There should be only one variable

Data
Results of the experiment
May be quantitative (numbers) or qualitative

Data
Must be organized
Can be organized into charts, tables, or graphs

Conclusion
The answer to the hypothesis based on the data obtained from the experiment

Retest
In order to verify the results, experiments must be retested.

Review