Hypothesised null value for confidence interval of relative risk
Correct Answer: One
Description: RELATIVE RISK Relative risk (RR) is the ratio of the incidence of the disease (or death) among exposed and the incidence among non-exposed. Some authors use the term "risk ratio" to refer to relative risk. Estimation of relative risk (RR) is impoant in aetiological enquiries. It is a direct measure (or index) of the "strength" of the association between suspected cause and effect. A relative risk of one indicates no association; relative risk greater than one suggests "positive'.' association between exposure and the disease under study.Hypothesised null value for confidence value is arbitrarily taken as 1. A relative risk of 2 indicates that the incidence rate of disease is 2 times higher in the exposed group as compared with the unexposed. Equivalently, this represents a 100 per cent increase in risk. A relative risk of 0.25 indicates a 75% reduction in the incidence rate in exposed individuals as compared with the unexposed It is often useful to consider the 95 per cent confidence interval of a relative risk since it provides an indication of the likely and maximum levels of risk. In our hypothetical example the relative risk is 10. It implies that smokers are 10 times at greater risk of developing lung cancer than non-smokers. The larger the RR, the greater the "strength" of the association between the suspected factor and disease. It may be noted that risk does not necessarily imply causal association. Ref : Park 23rd edition Pgno : 78
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