1.2 Research Methods AP Psychology

Methods for studying behavior… Experimental method Surveys Naturalistic observation Case study Longitudinal method Cross-sectional method Correlational studies

Experimental Method Carefully controlled method of investigation used to establish cause-effect relationship The experimenter purposely manipulates and controls selected variables

Testable Hypothesis Hypothesis – statement that describes the relationship between two or more variables Must be testable, verifiable, and refutable Null Hypothesis – no new findings / no new relationship

Hypothesis

Null Hypothesis

IV vs. DV Independent Variable – factor that is manipulated or controlled by the experimenter (aka explanatory variable) Dependent Variable – factor that is measured by the experimenter (aka response variable) Tips… IV influences DV Manipulate the IV, measure the DV Dependent on the independent If _________ (IV) then ___________ (DV). How the______ affects the _____. IV DV

IV vs. DV Examples An experimenter wants to determine if playing violent video games increases the frequency of aggressive behavior in children. IV – the type of video game DV - the amount of aggressive behavior An experimenter wants to determine the relationship between rehearsal/repetition of a list of definitions of difficult SAT vocab words and later recall of these definitions IV – the amount of rehearsal/repetition DV – recall of correct definitions

IV vs. DV Examples An experimenter wants to determine if a new drug reduces hyperactivity in children. IV – drug DV – level of hyperactivity

Extraneous Variables Aka – confounding / lurking / hidden Factor that the researcher failed to control or eliminate (damage the validity)

Operational Definitions Precise description of how the variable in a study will be manipulated and measured

Operational Definition

Participants in Experiments Experimental Group – the participants who are exposed to the IV Control Group – the participants who are exposed to all experimental conditions except the IV

Experimental Controls Purpose – ensure all groups in the experiment are treated exactly the same, except the IV Limit lurking variables!

Problems with Experiments Experimenter Bias – when a researchers expectations about the outcome influence the results Sample Bias – participants are not representative of the larger population Aka selection bias Volunteer Bias – differences between those willing to participate and those who don’t

Solutions to Problems Random Assignment – participants are assigned to EG or CG by chance Minimizes pre-existing differences between groups Placebo – an inactive substance or fake treatment used as a control ( Placebo Effect Single-Blind Study – subjects don’t know whether they are the EG or CG Double-Blind Study – neither the researcher nor the participants know which is the EG Eliminates experimenter bias

Advantages of Experiments Identify cause-and-effect relationships Distinguish between real and placebo effects Can control bias (double-blind) Manipulate the IV; measure the DV Replication of study; increase confidence in results (IV influences DV)

Disadvantages of Experiments Artificial lab vs. real life Confounding variables could cause results Biases (researcher or participant) Ethical concerns when subjects are deceived Informed consent

Descriptive Research Methods that enable researchers to observe and describe behaviors without manipulating DO NOT establish cause-and-effect