Evaluate, including the relative strengths Evaluate, including the relative strengths and weaknesses, of Field experiments and weaknesses, of Field experiments including their use in criminological including their use in criminological psychology with regard to :psychology with regard to :

Reliability Validity Ethics

.

Methodology/How Science Worksa Describe research methods used to assess witness

effectiveness including the laboratory experiment and the field experiment.

b Evaluate, including the relative strengths and weaknesses, the research methods listed in a above including:– their use in criminological psychology, reliability, validity and

ethical issues.

Note: In examination, students may be asked about the methods used in the application and asked to describe and evaluate, drawing on other methods both within the application and the five psychological approaches in AS. Eg observation(all types) questionnaires surveys, correlation, case studies & natural experiment

STOP! Evaluate

ReliabilityReliability• Field experiments are usually controlled to some extent

and all procedures are clearly written up giving a full explanation of everything that is done. This means that sometimes they are repeatable so that reliability can be checked. However…this is not always the case.

• Yuille and Cutshall used a real robbery for the field study and another case would be unlikely to be similar enough to repeat and compare for reliability.

• There are, when necessary internal reliability measures taken to ensure that all observers / interviewers / experimenters follow the exact same procedures. And so Internal reliability should be good.

• There are very few field experiments in EWT research and so there is not a large body of evidence showing reliability amongst field experiments in general unlike laboratory experiments where there is reliability/corroboration amongst very similar research.

ValidityValidity• Validity is considered to be a strength of the

field experiment. It is conducted in a real life natural situation, therefore ecological validity is usually high.

• Factors such as arousal levels or use of the senses which are a problem to emulate in lab experiments are far more true to life in this type of study.

• However the experimenter may still be manipulating the independent variable and in doing so is likely to add an artificial element that may impact the results and reduce validity

Ethics Ethics • In Lab experiments the eye witness knows

there are no real consequences faced by people because of evidence they give.

• However, real life eyewitnesses know their evidence can affect others lives.

• It would be unethical to allow participants to think their testimony would actually be used in court.

• It is therefore really difficult to test EWT in a field experiment

Ethics Ethics Field experiments are usually seen to be relatively

less ethical than lab experiments for a number of reasons:

1. Participants are not usually given the opportunity to give fully informed consent (Hofling) although sometimes they are as in the Yuille &Cutshall study.

2. Deception is a regular feature of many field experiments and is often necessary to test the I.V. – true of Hoffling and Yuille & Cutshall

• Reminding people of their right to withdraw is also a problem because sometimes they are being observed without them knowing as part of the D.V. (Hofling)

• Also some field experiments such as Yuille & Cutshall, require participants to recall events that may well have been extremely distressing. This could have an affect a persons mental and physical wellbeing

• How did Yuille & Cutshall over come this problem?