In case-control studies, the odds ratio is used as an estimate of the relative risk. In order for this approximation to be reasonable, some conditions must be met. Which of the following conditions is not necessary in order to use the odds ratio to estimate the relative risk?a. Cases are representative of all cases. b. With respect to exposure, controls are representative of the population to which you want to generalize your results. c. The exposure in question is rare in the population. d. The event (disease) under study is rare in the population.

The conditions that are not necessary to use the odd´s ratio to estimate the relative risk are a. Cases are representative of all cases and c. The exposure in question is rare in the population.

Step-by-step explanation:

Case-control studies are an example of observational studies. In this kind of studies, people are selected because of the presence or absence of a sisease, searching for the previous presence of the suspected cause (exposure).  The idea is to select a group of people that has a particular condition or disease (the group of cases) and compare it with a group of persons that does not have this disease (the control group). Reasearchers analyse both groups and compare them in order to find some information related with the presence of previous or present exposure to factors that are considered as the cause of the disease. The variable used to estimate the relationship between the exposure and the development of the disease is called odd ratio and it is an aproximation of another variable "relative risk".

The odd ratio is aproximately equal to the relative risk (it means it is a good estimator) when the disease is not frequent on the population (in other words, the event under study is rare in the population) and when controls are representative of the population that give rise to the cases.

The point a. Cases are representative of all cases is a dessirable condition but could it not be present.

Finally c. The exposure in question is rare in the population is not necessary, the only factor that must be rare in the population is the disease.

Summarizing, points b and d are strictly necessary, c. is a dessirable condition and a. is not necessary.  

its kinda hard to answer this when we dont have all the information that we need.