Psychology Terms

non-directional (two-tailed) hypothesis

a
statement predicting only that one variable will be
related to another

Directional (one-tailed) hypothesis

a statement predicting the direction of a relationship between variables

null hypothesis

a testable statement saying that
any difference or correlation in the results is due
to chance, that is, that no pattern in the results
has arisen because of the variables being studied

Hypothesis

statement based on the aims of an investigation

alternative hypothesis (research hypothesis)

the testable statement
predicting a difference in the DV between level
of the independent variable in an experiment l&
a relationship between variables in a correlation

dependent variable

The factor in an
an experiment that is measured and is expected
to change under the influence of the
independent variable

Expirement

an investigation that allows
researchers to look for a causal relationship
an independent variable is manipulated and is
expected to be responsible for changes in the
dependent variable

Independent Variable

the factor
under investigation in an experiment that is
manipulated to create two or more conditions
(levels) and is expected to be responsible for
changes in the dependent variable

uncontrolled variable

a variable that either acts
randomly, affecting the DV in all levels of the
IV, or systematically, i.e. on one level of the IV
(called a confounding variable) so can obscure
the effect of the IV, making the results difficult to
interpret, the effects of which have not or cannot
be limited or eliminated

Experimental Condition

One or more situations in an experiment that represents different levels of the IV and are compared (or compared to a control condition)

control condition

a standard against which other conditions can be compared in a scientific experiment

Experimental design

The way in which participants are allocated to levels of the IV

Independent measures design

An experimental design in which a different group of participants is used for each level of the IV (condition)

Demand Characteristics

Features of the experimental situation which give away the aims. They can cause participants to try to change their behavior. This reduces the validity of the study.

Random Allocation

As a way to reduce the effect of confounding variables such as individual differences is, Participants are put in each level of the IV such that each person has an equal chance of being in any condition.

Repeated Measures Design

An experimental design in which each participant performs at every level of the IV.

Participant Variables

individual differences between participants (such as age, personality, and intelligence.) that could affect their behavior in a study that would hide or exaggerate differences between levels of the IV.

Confounding Variables

A variable that the experimenter did not account for initially that affected the differences between measured levels of the IV

Field experiment

an investigation looking for
a causal relationship in which an independent
variable is manipulated and is expected to be
responsible for changes in the dependent variable.
It is conducted in a normal environment for the
participants for the behavior being investigated
and some control of variables is possible

Generalize

To apply the findings of a study more
widely, e.g. to other settings and populations

Ecological Validity

the extent to which the findings
of research conducted in one situation would
generalize to other situations. This is influenced by
whether the situation (e.g. a laboratory) represents
the real world effectively and whether the task is
relevant to real life (has mundane realism)

Controls

ways to keep potential confounding
variables constant, for example between levels of
the IV, to ensure measured differences in the DV
are likely to be due to the IV, raising validity

Standardization

keeping the procedure for
each participant in a study (e.g. an experiment
or interview) exactly the same to ensure that any
differences between participants or conditions
are due to the variables under investigation
rather than differences in the way they
were treated

Reliability

the extent to which a procedure, task
or measure is consistent, for example, that it
would produce the same results with the same
people on each occasion

Validity

the extent to which the researcher is
testing what they claim to be testing

Replication

keeping the procedure and materials
exactly the same between studies when
attempting, for example, to verify results or to
enable other studies to use exactly the same
techniques to answer related questions

Pilot Study

a small-scale test of the procedure of
a study before the main study is conducted. It aims
to ensure that the procedure and materials are valid
and reliable so that they can be adapted if not

Operational Definition

the clear description of a
variable such that it can be accurately manipulated.
measured or quantified, and the study can be
replicated. This includes the way that the IV and DV
in experiments, and the co-variables in correlations,
are described

Placebo

A pill or procedure given to a patient
who believes it to be a real treatment which in
fact has no active
'ingredient', i.e. no active drug
in the case of a pill or no therapeutic value in the
case of an intervention

Order Effects

practice and fatigue effects are the
consequences of participating in a study more
then once, for example in repeated measures
design. They cause changes in performance
between conditions that are not due to the IV.
so can obscure the effect on the DV

Practice Effect

a situation where participants'
performance improves because they experience
the experimental task more than once, for
example due to familiarity or learning the task

Fatigue Effect

a situation where participants'
performance declines because they experience
the experimental task more than once, e.g. due
to physical tiredness or boredom with the task

Randomization

a way to overcome order effect
in a repeated measures design; Each participant,
'allocated to perform in the different levels of the
in a way that ensures they have an equal chance,
participating in the different levels in any order

Counterbalancing

a way to overcome the order effect
in a repeated measures design. Each possible order
of levels of the IV is performed by a different sub.
group of participants. This can be described as an
ABBA design, as half the participants do condition
A then B, and half do B then A

Matched Pairs Design

an experimental design
in which participants are arranged into pairs.
Each pair is similar in ways that are important to
the study and one member of each pair performs
in a different level of the IV

Laboratory Experiment

a research method in
which there is an IV, a DV, and strict controls. It
looks for a causal relationship and is conducted
in a setting that is not in the usual environment
for the participants with regard to the behavior
they are performing

Replication

keeping the procedure and materials
exactly the same between studies when
attempting, for example, to verify results or to
enable other studies to use exactly the same
techniques to answer related questions

Operational Definition

the clear description of a
variable such that it can be accurately manipulated.
measured or quantified, and the study can be
replicated. This includes the way that the IV and DV
in experiments, and the co-variables in correlations,
are described

Placebo

a pill or procedure given to a patient
who believes it to be a real treatment which in
fact has no active
'ingredient', i.e. no active drug
in the case of a pill or no therapeutic value in the
case of an intervention.