Gathered through your senses
A scientist notices something in their natural world
An example of an observation might be noticing that many salamanders near a pond have curved, not straight, tails
A suggested solution to the problem.
Must be testable
Sometimes written as If…Then… statements
Predicts an outcome
An example of a hypothesis might be that the salamanders have curved tails due to a pollutant in the moist soil where they live.
A procedure to test the hypothesis.
Variable – factor in the experiment that is being tested
A good or “valid” experiment will only have ONE variable!
Controls and Variables
An experimenter changes one factor and observes or measures what happens.
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.
Controls are NOT being tested
Controls are used for COMPARISON
The factor that is changed is known as the independent variable.
The factor that is measured or observed is called the dependent variable.