pjgscioisamazing wrote:Now how exactly can you tell teh difference between a case-control and a cohort study?
A case-control study is trying to find the cause/effect of something. For example, a case-control study could be when disease detectives are trying to find out why many people have lung cancer and most of them have past records of smoking. That is a cause/effect relationship.
Also, the scenario will be a case-control study if it says, "The cases" or "The controls" when describing the situtation.
Here is a case-control study taken from one of my tests:
Disease detectives considered the following products as possible sources of exposure: syrup-based medications, skin creams, herbal remedies, bath products, and tonics. Samples were analyzed by the CDC Environmental Health laboratory. Diethylene glycol, or DEG was detected in the syrups. Disease detectives began a study to identify which of the syrup medications was the cause of the outbreak. They talked to families of the children with renal failure, and with families of children who had been in the hospital for other types of illnesses. They asked questions that asked about types of medications used, and how often they were used by the children.
In the above study, you can see how the disease detectives were trying to find a cause/effect relationship. So, it is a case-control study.
A cohort study is when a group of people who share a common characteristic are studied. For example, if a bunch of people were born in November, then they will be part of a Birth cohort.
Here is a cohort study taken from one of my tests:
Disease detectives next conducted a study of 49 well children who have been given pain relief syrup from the contaminated lots. The children were monitored for a mean of 87 days from the last dose of contaminated syrup to determine possible illness from the syrup. All 49 children survived, and none developed signs or symptoms of DEG toxicity. However, some had finding on their lab tests for kidney and liver function that were evidence of sub-clinical toxic effect.
In the above study, the reason it is a cohort study is because:
-They are all well children who had been given pain relief syrup from the contaminated lots.
That is the common characteristic they share. So, it is a cohort study.
Once you get the hang of it, it is pretty easy to tell what type of study design the scenario is. One way to practice learning the different study designs would be to look at sample tests and whenever there is a study design question, look at the scenario and answer it.
Also, case-control studies are probably the most commonly used study designs.
Hope this helps!
