True experiments

• Experimenters decide on a single variable, the independent variable (IV) which they manipulate (or deliberately alter) in order to see whether this brings about a change in a second variable, known as the dependent variable (DV) which is measured in some quantitative way.
• All other variables which might affect the dependent variable are held constant (controlled) meaning any change in the DV can be said to have been caused by the IV and this means that the findings of experimental studies can be said to have strong internal validity.

Quasi-experiments

• Quasi means ‘seemingly’ or ‘apparently’ and quasi-experiments, therefore, share some but not all of the characteristics of a laboratory experiment; the defining feature is that it is not possible to randomly allocate participants to the experimental (treatment) and/or control groups, as these groupings are outside of the control of the experimenter.
• The researcher manipulates an independent variable.
• The fact that participants cannot be randomly allocated in a quasi-experiment means that the findings can be said to lack internal validity as there may be uncontrolled variables that led participants to be in one group and not the other, which are responsible for any changes in the DV.

Natural experiments

• Natural experiments are characterized by the fact that the independent variable is naturally occurring, i.e. the change between the experimental and control conditions is brought about as a consequence of factors which are outside of the experimenters' control, e.g. before and after the introduction of western TV channels on a remote island.
• As changes in the independent variable are naturally occurring, the findings of natural experiments may lack internal validity, as changes in the DV may have arisen due to extraneous factors, i.e. other societal changes which accompanied the introduction of Western TV were actually responsible for changes in the DV.

Field experiments

• Field experiments seek causal relationships between a deliberately manipulated independent variable and a measured or dependent variable yet they do not take place under controlled conditions; instead, they are conducted in real-world environments where participants can be found going about their daily business, e.g. at a cinema or shopping center.
• Participants in field experiments are often unaware that they are being observed as part of an experiment, meaning that their behaviour is more natural, while this increases the ecological validity of the findings, the inability to control extraneous variables due to the natural setting decreases internal validity

Naturalistic observation: covert

• The observer collects data from participants’ in their natural environments without any deliberate manipulation of the setting; while tallying can be used to collect quantitative data, the researcher may record qualitative ‘field notes’, describing behaviours of interest while diagrams and sketches may also be used.
• In a covert observation, participants are unaware of the observer and according to the BPS this is ethical if the study takes place in a public setting; data collected will be more credible as behaviour will be less inhibited and unaffected by demand characteristics or evaluation apprehension for example.

Naturalistic observation: non-participant

• The observer collects data from participants’ in their natural environments without any deliberate manipulation of the setting; while tallying can be used to collect quantitative data, the researcher may record qualitative ‘field notes’, describing behaviours of interest while diagrams and sketches may also be used.
• In a non-participant observation, the researcher remains separate from the activities of the group and does not interact with participants whilst conducting the observation; this lack of involvement means that the researcher is free to focus entirely on the data collection, arguably leading to a more accurate record of events.

Naturalistic observation: participant

• The observer collects data from participants in their natural environments without any deliberate manipulation of the setting; while tallying can be used to collect quantitative data, the researcher may record qualitative ‘field notes’, describing behaviours of interest while diagrams and sketches may also be used.
• In a participant observation the researcher becomes actively involved within the community or group that he or she is studying; this facilitates a unique perspective that would not have been otherwise possible and though this can lead to subjectivity, the credibility of the data may also be enhanced.

Unstructured interviews

• Unstructured interviews have a clear research objective and the interview schedule will include broad topics or themes for discussion; there may or may not be a list of starter questions but the defining features of this style of interview are flexibility and freedom; the direction of the interview is determined by the interviewee and the interviewer bases any questions asked on their previous responses.
• Unstructured interviewers need more training and experience to collect credible data; it can be hard to keep the interview on track and achieve the research objective when there is no ‘script’ as such; eliciting relevant information without asking leading questions and with minimal guidance in the interview schedule requires practice and skill.

Semi-structured interview

• A semi-structured interview is more flexible than a structured interview; while there is a pre-determined set of questions in the interview schedule, the interviewer may deviate from this, asking follow-on questions if the interviewee presents an unanticipated and relevant view; the interviewer may also rephrase questions and alter the order as appropriate.
• The semi-structured interview schedule may include both open and closed questions:  open questions prompt longer, richer answers from respondents allowing them to elaborate in their own words without being guided in any particular direction by the interviewer while closed questions result in brief, precise answers of just a few words.

Focus group

• A focus group comprises 8-12 people who are interviewed together about a topic of common interest; this size group works well allowing all members to have their say; people who share similar experiences tend to bond together, developing a sense of belonging and trust which helps them to talk freely about even sensitive issues.

• In a focus group, the researcher becomes the group facilitator and their role is to monitor the discussion, keep the group on the topic if they veer off into an irrelevant topic; they must ensure that all issues raised are responded to and explored as fully as possible within the time available.

• Correlational studies have no manipulated variable and therefore do not seek to establish causal relationships as is the case with experimental studies; they have two or more measured variables known as co-variables which are measured using quantitative data, e.g. through some sort of rating scale.
• Correlational studies are common in areas of psychology where it may not be possible to ethically or practically manipulate variables as part of an experiment; as there is no attempt to establish causality, internal validity relates solely to the extent to which the instruments used to measure the co-variables provide accurate and meaningful data.
• Correlational studies often use pre-established data sets - for example, the number of cigarettes sold per year in a country and the rate of heart-disease-related hospitalizations.

• Case studies typically focus on a single individual, group or organization that is unusual in some way; the researcher generally collects a detailed case history including secondary data from school reports or hospital records for example; this allows the researcher to gain necessary insight before collecting their own primary data.
• Case studies often comprise data that has been gathered using a variety of techniques including interview, observation, and the use of standardized tests for example. This is known as method triangulation and results in a rich and detailed insight into the behaviours of interest.