Quantitative Methods 2017

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Case control study: EXAMPLE

Major Coronary Events

Total number

Breast radiotherapy

Cases (n=963)

Controls (n=1205)

Left-sided breast cancer

543 (a)

601 (b)

1144

Right-sided breast cancer

420 (c)

604 (d)

1024

Total number

963

1205

2168

• Association can be tested by the Odds Ratio (OR): = ad / bc = 543*604 / 601*420 = 1.30 • Rare disease assumption (<5%)

Darby, et al. New Engl J Med 2013: 987-998