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