Can someone explain the difference between Cohort and Case Control? For instance, when one would be used as opposed to the other? I know one compares the exposed and non-exposed vs those with the disease and not - however, what is the real difference between Odds ratio and Relative Risk?
While they are used in two different scenarios, it's important to understand that they are basically the same thing, but from different "points of view." With odds ratio, you are comparing the odds of getting infected from the exposure, and with relative risk you are comparing the risk of being infected from exposure to the risk of being infected without exposure. They are basically trying to find the same thing. Besides knowing which type of study to use them in, you should also think which is necessary. In a case control, you are working backwards from the cases. You have determined (a) source, and you are trying to find the significance of that source in causing disease. With a cohort, you are working forward from the source, and to determine whether disease followed a certain path, you must find the significance of disease onset from that path.
In addition, I'd suggest also looking into things like absolute risk, and other measures of risk, such as excess risk, and risk difference.
Excess Risk: [(a+c)/a]-[(a+c)/b]
Risk Difference: [a/(a+c)]-[b/(b+d)]
Besides risk, and at a high school level, mathematics becomes extremely hard, and you'll be asked to both figure out and calculate numerous measures. Here are some I've commonly seen:
Cumulative Incidence Ratio: Number of new cases in a period of time / total population at risk (average population if changing w/time)
Point Prevalence: Cases in population / total population
Period Prevalence: Number of new cases in a certain time period / average population at the time
Case Fatality: Deaths / Total Population with disease [it's expressed per period of time]
Mortality Rate: Deaths / Total Population [it's expressed per period of time]
Rate Ratio: Incidence rate of a certain population / incidence rate of another population
And most of those should be expressed by per 10,000 or 100,000 people (whichever is specified or more appropriate)
If I wrote any of them wrong, please correct me, these are from the top of my head, and if there are others, please post them.