chapter 9- experimental studies

clinical trials

individuals randomized into two groups, only study design where you have randomization

community trials

communities/populations are assigned into 2 groups, typically non-randomly, unit of study is a group

clinical trials- objective

gold standard design for assessing cause-effect, intervention group gets new treatment, control group gets placebo

randomization 

a process whereby chance determines the participants’ likelihood of assignment to either an intervention group or a control group, each participant has an equal probability of being assigned to either group

the goal of randomization is ro

maximize comparability between the intervention and placebo group, only experimental studies use randomization, observational studies do not use it

prophylactic trial

designed to test preventative measures

therapeutic trial

evaluates new treatment methods

clinical trial- measure of association

participants are followed over time into the future, can calculate risk/incidence of the outcome and RR, differences in outcomes are also calculated

clinical trial- ethics

unethical to administer exposures that are known to be harmful, if intervention is observed as harmful or beneficial mid-way in the trial the trial stops

clinical trial phase I

Small scale studies to assess safety of the new drug/vaccine, doses, side effects, and reactions

clinical trial phase II

small study, heavy monitoring, assessing efficacy, does it work in controlled situations how it’s supposed to

clinical trial phase III

further evaluation of efficacy on a larger scale, also evaluate safety

clinical trial phase IV

evaluate long term safety and effectiveness in population (does it work in real world scenarios, conducted after approval and licensure

clinical trials- strengths

randomization maximizes comparability between groups, temporality between exposure and outcome is well defined, can assess risk of outcome, blinding is feasible

clinical trial- limitations

expensive, compliance may be difficult, loss to follow up

quasi-experminatal studies

a study where the investigator does not randomly allocate participants to the intervention and placebo group

community trials- objective 

useful for diseases that have their origins in social conditions that can be influenced by interventions directed at group behavior as well as individuals

community trials- strengths

directly estimate the realistic impact of intervention in a community, take advantage of natural experiments 

community trials- limitations

less control of entry into study and delivery intervention, fewer units to randomize, shifting composition of the community population, secular trends can muddy results