AS Psychology CIE Resource Methodology Variables and Reliability

AS Psychology CIE Resource Methodology: Variables and Reliability 1

Operationalisation of Variables The term operationalisation means being able to define variables simply and easily in order to Manipulate (IV) and Measure (DV) them. Example: Alcohol consumption and reaction time We could operationalise the IV as the number of alcohol units consumed. We could operationalise the DV as speed of response to a flashing light.

Pilot Studies These are small-scale “practice” investigations, where researchers can check all aspects of their research. They can then make changes or make improvements to the design and method. The aim of a pilot study is to improve the quality of the research, help avoid unnecessary work and save time and money. Participants may be able to suggest appropriate changes (for example admitting to demand characteristics).

Participant Variables Participants’ age, intelligence, personality and so on should be controlled for in an experiment… Name one research design that would allow you to do this…

Situational Variables It is important that the experimental setting and surrounding environment must be controlled for… This even includes temperature and noise!!! Name an experimental method that would allow you to control for situational variables…

Experimenter Variables The personality, appearance and conduct of the researcher may affect the results of the experiment!!!! Give an example of a study where the experimenter has influenced the results…

Internal Reliability Researchers try to produce results that are both reliable and valid. A test is reliable if it can be repeated under similar conditions and still yield the same approximate result – this is replication. This is essential in science - if a result is unreliable, it cannot be trusted and so will be ignored. However, results can be reliable but still be inaccurate. Research must also be valid, i. e. it measures what it’s supposed to measure.

There are two types of Reliability: Internal Reliability (Internal Consistency) Is it consistent within itself? External Reliability (Stability) Does it vary from one use to another?

Internal Reliability (Internal consistency) Is it consistent within itself? For example: Is it the same distance between 0 cm-1 cm as it is between 5 cm-6 cm and 8 cm-9 cm?

External reliability (stability) • Does it vary from one use to another? • For example: An IQ test should produce roughly the same measure for the same participant in October as it did in May (if the participants have not taken measures to increase their IQ!!)

Imagine giving a statement to the police. You might contradict yourself within the statement, damaging your internal reliability, or you might contradict yourself from one statement to the next, affecting your external reliability.

Internal Validity Results are internally valid if they’ve not been affected by any confounding variables. Are the results valid within the confines to the experimental setting? Various characteristics are required in order for an experiment to be internally valid. • No investigator effects • No demand characteristics • Use of standardised instructions

External (or ecological) validity • This refers to whether the results are valid beyond the confines of the experimental setting. • Can the results be generalised to the wider population, or to different settings, or different historical times?