Psychology- Chapter 2: The Research Enterprise in Psychology
*Research methods consist of various approaches to observation, measurement, manipulation, and control
of variables in empirical studies
- In order to generalize from the sample to the population, the sample must be representative of the
population. Opposite of representative is biased.
- Random sampling: each person in the population has an equal chance of being chosen for the
Looking for Causes: Experimental Research
- The experiment is a research method in which the investigator manipulates a variable under
carefully controlled conditions and observes whether changes occur in a second variable as a
- This is a powerful procedure that allows researchers to detect cause-and-effect relationships.
Psychologists depend on this method more than any other.
Independent and Dependent Variables
- X as the independent variable and Y as the dependent variable. We want to find out how X affects Y
- An independent variable is a condition or event that an experimenter varies in order to see its
impact on another variable. This is the variable in which the experimenter controls/manipulates.
- The dependent variable is the variable that is thought to be affected by manipulation of the
- The independent variable is called independent because it is free to be varied by the experimenter.
- The dependent variable is called dependent because it is thought to depend (at least in part) on
manipulations of the independent variable.
- (1) Independent variable- the variable that the experimenter changes or manipulates to see if it has
an effect on behaviour. I.e. Alcohol, changing the amounts to see if it has an effect on behaviour.
- (2) Dependent variable- the behaviour that is measured to see if the independent variable had an
effect. I.e. See how much of the alcohol was consumed and therefore measure the behaviour and
see if it had an effect. Dependent variable is dependent on the independent. EFFECT
- The effect of one independent variable depends on the effect of another
Experimental and Control Groups
- In an experiment, the investigator typically assembles two groups of subjects who are treated
differently with regard to the independent variable. These two groups are referred to as the
experimental group and the control group.
- The experimental group consists of the subjects who receive some special treatment in regard to
the independent variable. The control group consists of similar subjects who do not receive the
special treatment given to the experimental group.
- If the two groups are all alike in all respects except for the variation created by the manipulation of
the independent variable, any differences between the two groups on the dependent variable must
be due to the manipulation of the independent variable. In this way, the researchers isolate the ffect
of the independent variable on the dependent variable.
- Advantages: You can infer a cause and effect relationship.
- Extraneous variables are any variables other than the independent variable that seem likely to
influence the dependent variable in a specific study.
- A confounding of variables occurs when two variables are linked together in a way that makes it
difficult to sort out their specific effects.
- When an extraneous variable is confounded with an independent variable, a researcher cannot tell
which is having what effect on the dependent variable.
1 | P a g ePsychology- Chapter 2: The Research Enterprise in Psychology
- Random sampling/assignment: each person in the population has an equal chance of being chosen
for the sample.
Variations in Designing Experiments
- First, it is sometimes advantageous to use only one group of subjects who serve as their own control
group. The effects of the independent variable are evaluated by exposing this single group to two
different conditionsan experimental condition and a control condition.
- Second, it is possible to manipulate more than one independent variable in a single experiment.
- Third, it is also possible to use more than one dependent variable in a single study. Researchers
frequently use a number of dependent variables to get a more complete picture of how
experimental manipulations affect subjects behaviour.
Advantages and Disadvantages of Experimental Research
- Its principal advantage is that it permits conclusions about cause-and-effect relationships between
variables. Researchers are able to draw these conclusions about causation because the precise
control available in the experiment allows them to isolate the relationship between the independent
variable and the dependent variable, while neutralizing the effects of extraneous variables.
- Limitations of experiments: (1) The experiments are often artificial. Because experiments require
great control over proceedings, researchers must often conduct simple, contrived situations to test
their hypotheses experimentally. (2) Experimental method cant be used to explore some research
questions. Psychologists are frequently interested in the effects of factors that cannot be
manipulated as independent variables because of ethical concerns or practical realities.
Looking for Links: Descriptive/Correlational Research
- Descriptive/correlational research methods include observation, case studies, and su