Review of Research Methods

Overview of the Research Process

I. Develop a research question

II. Develop a hypothesis

III. Choose a research design

IV. Collect and analyze data

V. Make conclusions

I. Developing research questions

Sources of research ideas:

• Theory

• Previous research

• Casual observations

• Extraordinary events

• Social problems

Theory

• Theory- A summary statement that:– organizes what is known– explains existing data– helps us make testable predictions

• Theories attempt to answer several questions:– How are two or more variables related?– Why is this so?– Under what conditions does the relationship exist?

(Boundary conditions)

Developing Hypotheses

A hypothesis is a testable prediction.

Requires operational definition of concepts.

An operational definition specifies how the researcher plans to measure a concept.

Research Design

• Qualitative research- aim is to provide a rich description of a particular phenomenon or group.– E.G., interviews.

• Quantitative research- aim is to quantify relationships between variables.

Quantitative Research

A. Correlational studies: Studies that quantify the degree of relationship between two or more variables without manipulating the variables.

B. True Experiments: Studies that are intended to test cause-effect relationships between variables. At least one variable is manipulated.

Correlational Studies

• Correlation coefficient ranges from –1 to +1– Number (0 to 1) gives the strength of the

relationship• 0 = no correlation; 1 = perfect correlation• In practice, we use the following conventions:

.1 is small, .3 is medium, .5 is large

– Sign (+/-) gives the direction of the relationship

Interpreting Correlations

Correlation does not imply causation!

• Two problems in establishing cause-effect:– Directionality problem

• Does A cause B or does B cause A?

– Third variable problem• C may cause both A and B

Dealing with Correlational Problems

• Directionality:– Use a longitudinal design

• Third variable problem:– Measure the suspected third variables and

use a statistical procedure to hold them constant.

• E.g., partial correlation, multiple regression.

True Experiments

• Independent variable- the variable that is manipulated by the experimenter.– Experimental group- treatment– Control group- no treatment

• Dependent variable- the variable that is measured as an outcome.

Two Essential Ingredients of an Experiment

• Random assignment- each participant has an equal chance of being in each of the groups.

• Holding other variables constant- the only difference between groups should be the manipulated variable: Everything else must be held constant.

Factorial Design

• Factorial design- a design in which the levels of 2 or more independent variables are completely crossed.

• Main effect- a statistical term meaning that, overall, an independent variable has an effect on a dependent variable.

Interaction

• Interaction- a statistical term meaning that the effect of one independent variable on a dependent variable depends on the level of another independent variable.

Hypothetical Results of Factorial Design

0

1

2

3

4

5

6

7

High anger Low anger

Frustration

Control

Hypothetical Results of Factorial Design

00.5

1

1.52

2.53

3.54

4.55

High anger Low anger

Frustration

Control

Hypothetical Results of Factorial Design

00.5

1

1.52

2.53

3.54

4.55

High anger Low anger

Frustration

Control

Evaluating Research

• Internal validity: the degree to which a research finding provides clear or compelling information about causality.

• External validity: the degree to which a research finding provides an accurate description of what typically happens in the real world.

• Construct validity: the adequacy of the operational definitions. Did the researchers measure/manipulate what they intended to measure/manipulate?