A cue that makes participants unconsciously or consciously aware of the aims of the study or helps participants work out what the researcher expects to find
Internal - the degree to which an observed effect was due to the experimental manipulation of the IV rather than other factors eg confounding variables
External - the degree to which a research finding can be generalised to other settings, groups of people or other time periods
The IV varies naturally, the experiment takes advantage of a pre-existing variable - usually an event that has occurred. - can be in a lab or natural environment
Pros
allows research to take place that may be unethical otherwise
Identify categories eg age that make up a population and work out proportions needed for sample to be representative and participants are selected from strata using lottery technique
Pros
representative sample - generalisation is possible
Cons
cannot reflect all ways that people are different - complete representation is possible
Participants must be given comprehensive info concerning the nature and purpose of the research and their role in it - so they can make an informed decision on whether they want to participate
1. Participants should be given full details of the study - the aim of it and how the data will be used - only once they have this info they should be asked to formally indicate their agreement
2. Presumptive consent - gained from a similar group, if they agree, consent of other group will be presumed
3. Prior general - agreeing to be deceived, without knowing how