Research methods (Chap 1) [1/4]

experiment

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

Independent variable (IV)

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 (DV)

Dependent variable (DV)

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

Uncontrolled variables

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

Experimental condition

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

E.g. bright light vs dull light

Control condition

A level of the IV in an experiment from which the IV is absent. It is compared to one or more experimental conditions

E.g. Artificial light vs bright light

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 gives away the aims. They can cause participants to try to change their behaviour, for example to match their beliefs about what is supposed to happen, which reduces the validity of the study

Random allocation

A way to reduce the effect of confounding variables such as individual differences. 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 in 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 variable

An uncontrolled variable that acts systematically on one level of the IV so could hide or exaggerate differences between levels and therefore confuse the results making it difficult to understand the effect of IV on DV

Order effects

Practice and fatigue effects are the consequences of participating in a study more than once (Repeated measure 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 have experienced the experimental task more than once, e.g. due to boredom or tiredness.

Randomisation

a way to overcome order effects in a repeated measures design. Each participant is allocated to perform in the different levels of the IV in a way that ensures they have an equal chance of participating in the different levels in any order

Counterbalancing

a way to overcome order effects 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.

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

Standardisation

Keeping the procedure for each participant in a study (E.g am 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

Pilot study

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

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