Scioly.org

i have this really good packet and it says that prevalence is the number of cases/events/condition in a given population
so i guess it would be a or b on a 2x2 table
and for incidence it says the denominator is the population at risk, and the numerator is the number of new cases occuring
don't know the formula according to 2x2 table though
and for rate, it says it is the frequency with which an event occurs in a defined population (i have no idea what the formula would be though)

What's the difference between relative risk and risk?

relative risk is (a/a+b)/(c/c+d)
risk is : look above i dont feel like repeating my definition

Does anyone know the definitive difference between incidence and prevalence? Several websites suggest multiple, different differences, and I was wondering what the vote was here.

Aia wrote:Does anyone know the definitive difference between incidence and prevalence? Several websites suggest multiple, different differences, and I was wondering what the vote was here.

The basic difference is new cases versus existing cases. The problem is that there is incidence and incidence rate, prevalence and prevalence rate, and many people treat them as interchangeable when technically they are not. Point prevalence is number of cases existing at a given moment, period prevalence (which is usually just called prevalence) is number of cases which exist at any point during a defined period, and prevalence rate is number of cases in a period (or at a point, but usually a period) divided by the population under consideration. Incidence is number of new cases arising in a defined period; for incidence rate, you divide by the population. A Rate Ratio (which is actually also a measure of Relative Risk, although the latter usually means Risk Ratio) will be the quotient of either incidence or prevalence for the study population divided by the same measure for the general population.

There is really quite a but of slop in the use of terminology, which is probably why so many people have issues with it.

you would want to know the different types of studies- cohort, cross-sectional, randomized, etc.

in the past tests i've taken, there have been several questions about studies- but i'm from Texas and i don't know if they do it differently in other states...

also, if you haven't already, look at the training handouts on soinc.org- it has good information but i don't think that's enough if you want to medal in disease detectives...

does anyone have any good websites for practice tests that is not cdc.gov or soinc or something like that??
i have already gone through them
also how in depth should we study it??

Now how exactly can you tell teh difference between a case-control and a cohort study?

pjgscioisamazing wrote:Now how exactly can you tell teh difference between a case-control and a cohort study?

well case-control would be a study on two groups of ppl in the same enviroment but one group has a disease and the other group doesn't
and cohort would be case-control without the comparison

doctor wrote:does anyone have any good websites for practice tests that is not cdc.gov or soinc or something like that??
i have already gone through them
also how in depth should we study it??

Have you tried the site at Tufts?
As to how in-depth you should study... it depends on what test you're talking about. Regionals is usually just basic knowledge about everything. States and Nationals are more detailed, and there's usually more math involved in them. But then, it also depends on what state you're in - states tend to focus on different things.