Scientific Methods in Psychology

Why Study Methods?

-  Enhance Understanding of Research-Based Information

-  Critical Thinking About Research

-  Reduction of Participation Anxiety

Goals of the Scientific Enterprise

-  Measurement and Description

-  Gain knowledge

-  Describe psychological phenomena

-  Provide a pool of observations and data with which to generate hypotheses for further testing

-  Understanding and Prediction

- Begin to understand the phenomena we are studying.

- Predict when a behavior will occur and how it will manifest

-  When a behavior/phenomena is understood, then it can usually be predicted

-  Application and Control

- It is hoped that the research conducted will eventually have some practical application

- Gain some degree of control over the phenomenon

Research Methods in Psychology

-  Features

-  Theory

-  Much psychology research is driven by theory.
-  Theories through observation
-  Theories from past research
Theory: An interrelated set of ideas used to explain a phenomenon
-  Research conducted with relevant theories in mind.

-  Hypothesis

Hypothesis: A tentative statement about the relationship between two or more variables
-  Hypotheses can come from current theories
-  Hypotheses can come from careful observation

-  Operational definition

Operational definition : a definition that specifies the operations (or procedures) used to produce or measure something - a way to give it a numerical value
-  Describe actions or operations that will be made to measure or control a variable

-  Collect data/evidence

- Used to test hypotheses

- Techniques vary

- Source of data


- Population:The full set of every potential subject who falls into your category of interest

<>- Sample:  Small group of people who actually participate in the study

-Representative sample: Shares critical characteristics with the population of interest

- Biased sample:  Is not characteristic of the population of interest

- Statements about a population must be based on a sample that represents the population

- Random sample

- Does not rely on self selection

- Each member of population has an equal chance of being selected for the study

- Convenience sample

- Request volunteers from groups sharing meeting general requirements of the study

-  Naturalistic Observation

- Watching and recording behavior in its natural environment

- Can describe but not explain behavior

- Survey

- Ask people to report their behavior or opinions

- Common research method

- Potential pitfalls

- Wording of questions on survey

- Representativeness of sample

- Correlational Studies

- The use of statistical methods to examine the relationship between two or more variables

- Typically used when experimenters cannot exert control over the variables they want to study

Correlation: A measure of the relationship between two variables, which are both outside the investigator’s control

-  Nature of Correlation

-  Positive
- Indicates that there is a direct relationship between two variables
- High scores on one variable are associated with high scores on another variable
-  Low scores on one variable are associated with low scores on another variable
-  Negative
- Indicates that there is an inverse relationship between variables
- High scores on one variable are associated with low scores on another variable
-  Low scores on one variable are associated with high scores on the other variable

-  Strength of Correlation

Correlation coefficient: a numerical index of the degree of relationship between two variables
- Coefficient can range between -1 and +1.
-1 is a perfect inverse relationship
+1 is a perfect direct relationship
0 is no relationship whatsoever
-  The closer the correlation coefficient  is to 1 or –1, the stronger the relationship between the two variables of interest

-  Prediction

- The stronger the correlation coefficient, the better you can use scores on one variable to predict the other

-  Advantages

- May be possible to clarify relationships between variables that cannot be examined by other methods
- Allow us to predict behavior to a certain extent

-  Disadvantages

- Correlation does not imply causation
- Does not allow researchers to draw conclusions about cause-effect relationships

-  Experimental Research

- To determine causal relationships it is necessary to conduct an experiment.

Experiment:  A research method in which the investigator manipulates a variable under carefully controlled conditions and observes whether any changes occur in a second variable as a result

-  Variables

-  Independent variable
Independent variable: a condition or event that an experimenter varies in order to see its impact on another variable
- The variable the experimenter manipulates
-  Dependent variable
Dependent variable: the variable that is thought to be affected by the manipulation of the independent variable
-  Subject  variable
Subject variables: individual differences between people
-  Often affect the behavior of the dependent variable
-  Cannot be manipulated by the experimenter
-  Try to make sure each of the experimental groups match on subject variables

-  Experimental and Control Groups

-  Experimental group
Experimental group: consists of subjects who receive some special treatment in regard to the independent variable
-  Control group
Control group: subjects who are treated similarly to those in the experimental group but who do not receive the special treatment regarding the independent variable
- It is crucial that the experimental and control groups be exactly equal on all counts except for manipulation of the independent variable

-  Extraneous Variables

Extraneous variables: any variables other than the independent variable that seem likely to influence the dependent variable in the specific study

-  Advantages

-  Precisely determine relationship between variables
-  Control
-  Systematic

-  Disadvantages

-  Artificial
-  Experimenter Bias and Demand Characteristics
-  Experimenter Bias
Experimenter bias: the tendency of an experimenter to unintentionally distort the procedure or results of an experiment based on the expected outcome of the study
Blind observer: an observer who can record data without knowing what the researcher has predicted
-  Demand characteristics
Demand characteristics: cues that tell a subject what is expected of him or her and what the experimenter hopes to find
-  Placebo effect
-  Can occur when subject’s expectations cause them to experience some change even though they receive empty, fake, or ineffectual treatment.
- Single blind study: When either the observer or the subject does not know which subjects received which treatment
- Double blind study:  A study in which both the observer and the subjects are unaware of which subjects received which treatment