Question

Epidemiologic case-control studies often report increased risk of an event given exposure, but we know that we can only calculate the odds ratio in a case-control study as opposed to a risk ratio.

Is it important to distinguish between a risk ratio and an odds ratio?

When does Odds Ratio approximate the Risk Ratio?

When does it approximate the Rate Ratio?

Answer 1

ANSWER::

When two groups are under study or observation .then we can choose above ratio. which are considered as

1) Odds Ratio It is defined as the ratio of the odds of an event occurring in one group to the odds of it occurring in another group or to a sample-based estimate of that ratio

= [A/(1-A)]/[B/(1-B)].

2. Relative risk (RR) is the risk of an event (or of developing a disease) relative to exposure=A/B

• The odds ratio is very similar to the risk ratio,
• A relative risk is much easier to interpret and makes much more sense
• A relative risk  is for the high er probabilities
• The odds ratio  smaller one to show an association between events

Risk Ratio is the same as Relative Risk

Risk    -        Risk is the probability that an event will happen latter

therefore Relative risk         =       no of events happened / Total no of risk

Relative risk requires calculation of incidence rates in population at risk and therefore, it is used in statistical analysis of cohort studies.

Odds ratio does not require the calculation pof incidence rates and therefore used in case-control studies

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