Odds Ratio Assignment

Odds Ratio Assignment

Odds ratio is a measure of association between an exposure and outcome.

OR= [ (n) exposed cases/ (n) unexposed cases] ÷ [ (n) exposed non-cases/ (n) unexposed non- cases ]

OR= [ (n) exposed cases × (n) unexposed cases] ÷ [ (n) exposed non-cases × (n) unexposed non-cases]

Table

OR= ad/ bc = (64×117) ÷ (56 × 27) = 4.9524

OR                  4.9524

95% CI            2.8541 to 8.5934

Z statistic        5.690

P< 0.0001

Odds of having lung cancer is 4.9524 higher for people exposed to tobacco smoke compared to those not exposed to tobacco smoke (Sheskin, 2004).

Vitamin D supplements and prostate cancer

OR                0.49

95% CI            0.45 to 0.60

P= 0.001

Odds ratio means that the odds of using vitamin D supplements is 0.49 higher in prostate cancer patients compared to non-prostate cancer. 95% confidence interval estimates the precision of the odds ratio whereby there is 95% confidence that the odds ratio would fall between the intervals of 0.45 to 0.60

Odds ratio is a single measure of association and using it does not meaningfully describe an individual’s ability in classifying subjects (Sheskin, 2004). It is also often confused with relative risk in medical literature due to difficulty in comprehending it.

Reference

Sheskin, D. J., (2004). Handbook of parametric and non-parametric statistical procedures (3^rd       Ed.).  Boca Raton: Chapman and Hall/ CRC .

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