Identify an independent variable in this experiment. The source of the periwinkles (northern or southern sites in the Gulf of Maine) The shell thickness of the periwinkles The shell thickness of the crabs The number of periwinkles killed by crabs
Answer (1)
In this experiment, the independent variable is the 'source of the periwinkles (northern or southern sites in the Gulf of Maine)'.
To understand why this is the independent variable, let's define what an independent variable is:
An independent variable is the factor in an experiment that is changed or controlled by the researchers to test its effects on the dependent variable(s). It is the cause that can be manipulated to observe how the changes affect other variables in the experiment.
In this context:
Source of the periwinkles : This is being manipulated by choosing periwinkles from either northern or southern sites in the Gulf of Maine. By selecting different sites, researchers can observe if there are any changes in other variables.
The shell thickness of the periwinkles , shell thickness of the crabs , and number of periwinkles killed by crabs are dependent variables. These are potential outcomes that could change based on the manipulation of the independent variable, which is the source of the periwinkles.
In summary, since the 'source of the periwinkles' is the condition being altered and tested for its impact, it is the independent variable in this experiment.
