experience leading you to your own conclusions, possibly allowing contradicting statements to be "true"
the Hawthorn effect/ Participant bias
just by virtue of knowing that you are in an experiment, you will act differently under the conditions of the experiment rather than you would behave normally.
Longitudinal Studies
progressively re testing the same group in increments
really accurate
expensive
lose participants
takes forevah!
Cross-sectional studies
look at separate groups in different age categories all at once with the same IV
quick, but has A LOT of confounding variables
Cohort-Sequential study
a research method in which a cross section o the population is chosen and then each cohort or group is followed for a short period of time.