AS revision notes


Research methods

Directional hypothesis – specifically states the direction of the results as it predicts the nature or direction of the outcome. (one tailed hypothesis)

Non-directional – Direction of results is not predicted, can go either direction (two tailed hypothesis)

Null hypothesis – No relationship between the variables being investigate. A null hypothesis is used because it makes a precise prediction that can be disproved, supporting the alternative hypothesis

Alternative hypothesis – Any hypothesis that is not the null hypothesis

Operationalising variables – once the null and alternative hypothesis has been written the experimenter has to operationalize their variables. This is the process of devising a way of measuring a variable.

Reliability – two or more measurements or observations of the same psychological event will be consistent with each other.

Internal validity – has internal validity if the outcome is the result of the variables that are manipulated in the study.

External validity – the extent to which findings can be generalised to settings other than the research setting

Face validity – simply involves an eyeball test, does it look as if its measuring what it should be?

Concurrent validity – involves comparing the results by a new test to an older test.

Predictive validity – ability of the test to predict performance on future tests


Independent variable – the variable that the researcher manipulates and which is assumed to have a direct effect on the dependant variable (CAUSE)

Dependant variable - the variable that is affected by changes in the independent variable (EFFECT)

Extraneous variables – this is a general term for any variables other than the IV that might affect the DV

Demand characteristics – cues in the environment that help the participant work out what the research hypothesis is.

Internal validity controlled by: Single blind technique – a procedure in an experiment where the participants do not know the hypothesis and do not know which condition they are in

Investigator effects – the influence of the researcher whereby their expectations of what the research outcome should be could lead to a self- fulfilling prophecy.

Internal validity controlled by: Double blind technique – where neither the participants nor the research assistant know the hypothesis or the condition they are in

Target population and sampling

Random: A sample in which every member of the target population has an equal chance of being selected

Methods: Names drawn out of a hat, computer generated, numbered list and a number table.

Population validity: representative sample with high population validity

Opportunity: A sample that consists of those people available to the researcher

Methods: researcher would approach people and ask them to take part. Taking advantage of whoever happens to be available

Population validity: High chance sample will be biased, low population validity

Volunteer: A sample where the participants self-select. Volunteering to take part

Method: The researcher…


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