A research design in which a group of participants is selected without regard to risks and is followed repeatedly to determine factors related to developmental outcomes or later onset of diseases or other conditions (see below for a more technical definition). They are, thus, a form of longitudinal studies. The unit of analysis can vary from an individual to collectives such as households and business organizations. They differ from cohort studies that sample and follow up an age cohort born in particular month and year whereas panel studies sample from an entire age range and follow up repeatedly, typically across the life course, thus involving multiple cohorts of different ages. A well-known example of a panel study is the British Household Panel Survey that begin in 1991, with panel 1 consisting of about 5500 households and 10300 individuals drawn from 250 areas in the UK. Panel studies, like any other research design, have both advantages and disadvantages. Advantages include the fact they can be used for studies that are a mixture of quantitative and qualitative data, and provide a relatively quick method of assembling a representative sample for consultation (in other words, they can be cost-effective). One disadvantage is that panel members can become increasingly informed over time (e.g., by exposure to the media), with the consequence that their responses become atypical. Another is panel attrition (e.g., panel members leaving or not responding). Both these disadvantages apply to other longitudinal designs. Technically, the design of panel studies can be defined as the longitudinal collection of information on a set of individuals (N) at multiple occasions (T) where the number of persons far exceeds the number of occasions (N>T*k; i.e. N>1,000 and T=2, so k=500).
See Autoregressive series/model, Attrition, Cohort, Follow-back design, Longitudinal design, Longitudinal studies, Multiple cohort study, Prospective cohort