Psychology - Research Methods

experimental method, control of variables, experimental design, types of experiment, sampling, and ethical issues for AQA Psychology

experimental method

a process involving the manipulation of an independent variable to measure the effect on the dependent variable

aim

a general statement of what the researcher intends to investigate

hypothesis

a clear, precise, testable statement that states the expected relationship between the variables to be investigated. stated at the outset of any study.

directional hypothesis

states the expected direction of the difference or relationship between the variables to be investigated

non-directional hypothesis

does not state the expected direction of the relationship between the variables to be investigated

variables

a condition in an experiment that can take on different categories, levels, or values and that can be quantified

independent variable

an aspect of the experimental situation that is manipulated by the researcher - or that changes naturally - so the effect on the dependent variable can be measured

dependent variable

an aspect of the experiment that is measured by the researcher and is affected by the manipulation of the independent variable

operationalisation

clearly defining variables in terms of how they can be measured

extraneous variable

any aspect of an experiment other than the independent variable that may have an effect on the dependent variable if it is not controlled

confounding variable

an unmeasured aspect of an experiment that influences the relationship between an independent and a dependent variable - so we cannot be sure of the true source of changes to the dependent variable

demand characteristics

any cue from the researcher or from the research situation that may be interpreted by participants as revealing the purpose of the investigation and which may lead to the participant changing their behaviour within the research situation

investigator effects

any effect of the investigator’s behaviour on the research outcome

randomisation

the use of chance in order to control for the effects of bias when designing materials and deciding the order of conditions

standardisation

using exactly the same formalised procedures and instructions for all participants in a research study

experimental design

the different ways in which the testing of participants can be organised in relation to the experimental conditions

independent groups design

participants are allocated to different groups where each group represents one experimental condition

repeated measures

all participants take part in all conditions of the experiment

matched pairs design

pairs of participants are first matched on some variables that may affect the dependent variable. then one member of the pair is assigned to condition A and the other to condition B.

random allocation

an attempt to control for participant variables in an independent groups design which ensures that each participant has the same chance of being in one condition as any other

counterbalancing

an attempt to control for the effects of order in a repeated measures design: half the participants experience the conditions in one order, and the other half in the opposite order

laboratory experiment

an experiment that takes place in a controlled environment within which the researcher manipulates the independent variable and records the effect on the dependent variable, whilst maintaining strict control of extraneous variables

field experiment

an experiment that takes place in a natural setting within which the researcher manipulates the independent variable and records the effect on the dependent variable

natural experiment

an experiment where the change in independent variable in not brought about by the researcher but would have happened even if the researcher had not been there

quasi-experiment

an ‘experiment’ which contains a naturally occurring independent variable which is a difference between people that already exists (e.g. age, gender). the researcher examines the effect of this variable on the dependent variable.

population

a group of people who are the focus of the researcher’s interest, from which a smaller sample is drawn

sample

a group of people who take part in a research investigation

sampling technique

the method used to select people from the population for research

bias

when certain groups may be over- or under-represented within the sample selected

generalisation

the extent to which findings and observations from an investigation can be broadly applied to the population

random sampling

a form of sampling in which all members of the target population have an equal chance of being selected

systematic sampling

a form of sampling in which every nth member of the target population is selected

stratified sampling

a form of sampling in which the composition of the sample reflects the proportions of people in certain sub-groups (strata) within the target population

opportunity sampling

a form of sampling where participants include anyone who happens to be willing and available

volunteer sampling

a form of sampling which involves participants selecting themselves to be part of the sample