research methods experimental glossary

Experimental method

the manipulation of an independent variable to measure the effect on the dependent variable

hypothesis

a clear precise testable statement that states the relationship between the variables to investigate

directional hypothesis

hypothesis that states the direction of the difference or relationship

non-directional hypothesis

hypothesis that does not state the direction of the difference or relationship

null hypothesis

hypothesis that predicts no effect of the IV on the DV

independent variable

some aspect of the experimental situation that is manipulated by the researcher or changes naturally so that the dependent variable can be measured

dependent variable

the variable that is measured by the researcher. any effect on the DV should be caused by the change in the Independent Variable

extraneous variables

any variable other than the independent variable that may affect the dependent variable if it is not controlled.

randomisation

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

standardization

using exactly the same formalised procedures and instructions for all participants in a research study so as to avoid investigator effects caused by different instructions

confounding variables

a kind of EV but the key feature is that a confounding variable varies systematically with the IV therefore we can’t tell if any change in the DV is due to the IV or confounding variable

operationalization

clearly defining variables in terms of how they can be measured

laboratory experiment

an experiment that takes place in a controlled environment within which the researcher manipulates the IV and records effect on DV whilst maintaining strict control of extraneous variables.

field experiment

an experiment that takes place in a natural setting within which the researcher manipulates the IV and records the effect on the DV

natural experiment

an experiment where the change in the IV is not brought about by the researcher but would have happened even if the researcher had not been there. the researcher records the effect on a DV they have decided on

quasi experiment

a study that is almost an experiment but lacks key ingredients - IV is not determined by anyone but simply exists.

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. the sample is drawn form a target population and is presumed to be representative of that population.

random sampling

a sample of participants produced by using a random technique such that every member of the target population has an equal chance of being selected.

opportunity sampling

a sample of participants produced by selecting people who are most easily available at the time

stratified sampling

a sampling technique in which groups of participants are selected in proportion to their frequency in the population in order to obtain a representative sample

systemic sampling

a method of obtaining a representative sample by selecting every nth person

independent groups design

two separate groups participate in the study at the same time, and do different experiments as the other group, which helps reduce order effects

repeated measures design

the same group of people does both experiments, which is cheaper and controls variables within the participants, but might cause order effects

matched pairs design

the participants are matched into pairs based on variables according to the experiment and one half of the pair does one experiment and the other does the other.

Counterbalancing

way to resolve order effects, especially in the repeated measures design

random allocation

randomly assigning participants to each experiment in independent groups design, which helps ensure an even selection

order effects

a potential change in the results of the experiment as a result of the order that the participant did the experiment in

pilot study

a small scale experiment done before the main experiment in order to review and alter elements

control group

a group that doesn’t have any experiment, in order to compare results

experimental group

a group that does participate in the experiment by receiving the variable

informed consent

participants must be completely aware of all aspects of the experiment and must give consent knowing all that information

confidentiality

participants data and information must be protected by the researcher

right to withdraw

participants must be able to withdraw from the experiment at any time and must know of their right to do so

protection from harm

participants should not be subject to any more psychological or physical harm than they would be on a daily basis

debriefing

after the experiments, participants must be informed of any and all information to do with the experiment, especially if it has previously been withheld for the purpose of the experiment