The Science of Psychology The Scientific Method and Research Design

Experimental Research  With experimental research, one can determine cause and effect among variables.  Experiments allow researchers to manipulate or control one variable to observe the effect of that manipulation on another variable, while holding all other variables constant.

More on Experimental Research  There are several terms you need to memorize regarding experimental research.

Hypothesis  A statement about the relationship between two or more variables  Must be testable

Key Terms - Variables  Variables- Factors that change in an experiment Independent Variable (IV)- The factor that the experimenter manipulates or changes Dependent Variable (DV)- The factor being measured Extraneous or Confounding Variable- An undesirable variable that influences the relationship between the IV and DV, though it is not the variable of interest.  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. Ex post facto – Research in which we choose subjects based on a pre-existing condition.

Key Terms – People Involved  Subjects- Animals or humans used in your study  Participants- Humans used in your study  Confederate – Someone who is in on the experiment but pretends to know nothing about it  Population- The large group containing all potential participants for your study (can be defined in many ways)  Sample- Small subgroup of participants chosen from the larger population

Key Terms – People Involved  Experimental Group- The group that experiences the IV; OR the group on which the critical part of the experiment is performed  Control Group- The group that does not experience the IV; OR the group that does not participate in the critical part of the experiment

Key Terms - Locations  Lab setting- Gives the researcher greater control over variables, but may not be a perfect replication of the real-world environment  Field setting- Gives a more natural look at the participants because they are in their natural habitat, but the researcher has less control

Key Terms – Control Measures  Single-Blind: subject unaware of assignment  Double-Blind: subject and experimenter unaware of placement  Randomization Random Sampling  To randomly select participants from population  Allows you to generalize results Random assignment  To randomly divide participants into groups  Either the _____________ or _____________ group