Qualitative methods are not easy to replicate because much of what is found will be specific to a participant due to how the interviewer, for example, responds to their answers. Examples of this type of method include case studies and unstructured interviews both of which do not really test a hypothesis like in a laboratory study but enable researchers to find out things like why someone behaves in a certain way or how they feel about a subject. When qualitative methods are used, this means that researchers are trying to collect lots of rich, detailed information in order to explore a subject or theory in more depth. Reliability and validity of qualitative methods

Similarly, in a repeated measures design, participants are more subject to demand characteristics because some are able to work out what the researcher wants to find and may change their behaviour to meet this This can happen in a repeated measures design if counterbalancing is not used – participants ‘learn’ how to carry out a task and therefore their true ability is not being tested.

Validity in experimental design: the way in which participants are allocated to a study’s condition may affect the validity of what is found.

Validity in sampling methods: if there is an error in the sampling method then the results of the research will not accurately reflect the target population and this will mean that there is a problem with the study’s external validity.

Therefore, it is vital that a research study is designed in a way that will not affect either internal or external validity. A study which focused on men would not be valid as it is not measuring what it sets out to measure – it would be seen to lack external validity. If the same research were looking at body language amongst women then they are the target population. For example, if a study was set up to measure how much people communicate via body language, then the way in which the research is set up must ensure that it is body language which is being tested this is known as internal validity. Validity refers to the extent to which research measures what it has actually set out to measure. Validity is different to reliability and you will need to be able to clearly differentiate between the two.

Reliability in research example