# Relative Risk Ratio Analysis

Risk is a probability; odds on the other hand are chances or a ratio, Probability is the likelihood of an event or outcome to occur in relation to all possible events or outcomes. For example, by flipping a coin, the risk that you will get heads is 1 win out of 2 total possible outcomes or 50%.

Relative risk and also called risk ratio compares risk of an event or exposure with those without exposure, e.g. the relative risk of getting caries for sugar consumers compared to non-sugar consumers. Relative risk depends on the incidence of an event given that we already know the exposure state of its participants. It can

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For example, if we have two groups “experimental and control” both are divided according to the outcome to occur or not, as experimental group with outcome occurring “group a”, experimental with outcome not occurring “group b”, control with outcome “group c” control with no outcome “group d”

RR = AR in experimental / AB in control = (a/ a+b) / (c/ c+d)

Odds on the other hand is the probability of an event or outcome over the probability of a certain event or outcome not occurring.

The odds ratio is the “ratio of ratio”, it compares the presence to absence of an exposure that already had a known outcome. For example, Presence to absence ratio of smoking cigarette in those who have brown teeth staining compared with the same ratio in those who don’t have brown teeth staining. It can be calculated even if we don’t know the probabilities in the groups. That is why odds ratio can be used to interpret the results of case control as well as prospective cohort