How should I structure an essay question asking me to evaluate a study?

A great acronym to remember when doing a longer essay question requiring you to evaluate a study is GRAVES.

This stands for Generalisability, Reliability, Applicability, Validity, Ethics and Subjectivity. These are all key areas realted to any psychological study that you might be asked to discuss. Taking two or three points from each of these areas should give you enough detail to include in an essay.

As a very popular example, let's take Milgram's (1963) study of obedience. The following is an example of some points you could include in a GRAVES essay plan:

G - predominantly white, male participants so the study lacks generalisability to the wider population, as all participants were American it is ethnocentric to Westernised cultures

R - the procedure was standardised for each participant, the same materials were used for each participant, the procedure was repeated with female participants so there is replicability

A - the study was a laboratory experiment and therefore does not accurately reflect real life social situations in which individuals are likely to be obedient 

V - the study lacks ecological validity due to the nature of the experiment, it is also unclear whether participants were displayig demand characterisitcs rather than obedience in that they may have just been complying with the researcher

E - the study deceived participants and may have caused significant emotional distress due to the nature of what they were doing

S - the study was not subjective, the method was operationalised and did not rely on interpretation from the researchers

You can use these points in the body of an essay as your main evaluation points after a brief description of the study.