Objective:

• Provided notes, an activity, and field observations SWBAT compare and contrast research methods and determine the difference between independent and dependent variables.

Notes Friday September 19, 2014

Experiments

• Direct way to test a hypothesis about a cause-effect relationship between variables

• One variable is controlled by the experimenter• e.g., democratic vs. authoritarian classroom

• The other is observed and measured• e.g., cooperative behavior among students

Experimental Variables

• Independent variable • the controlled factor in an experiment – what the

experimenter manipulates• hypothesized to cause an effect on another variable

•Dependent variable• the measured facts/data • hypothesized to be affected

Independent Variable

•Must have at least two levels• categories - male vs. female• numeric - ages 10, 12, 14

• Simplest is experimental vs. control• experimental condition gets treatment

(e.g., gets the new drug)• control condition does not

(e.g., gets the placebo)(created when using a double-blind procedure)

Extraneous Variables

• Extraneous Variables are undesirable variables that influence the relationship between the variables that an experimenter is examining

• Another way to think of this, is that these are variables the influence the outcome of an experiment, though they are not the variables that are actually of interest.

Extraneous Variables

• These variables are undesirable because they add error to an experiment. A major goal in research design is to decrease or control the influence of extraneous variables as much as possible.

An Example:

• Say you wanted to work out how clever a fish species were in finding food depending on how long since they had eaten. But if their ability to find food also depended on the temperature of the water and you were not able to either control or measure accurately the temperature of the water. Then the temperature could be described as an extraneous variable.