In a mass screening 1,329 men aged 40-59 years were examined with regard to serum cholesterol and systolic blood pressure, and then followed over a 6-year period for the development of coronary heart disease (CHD). At the beginning of the period all were free from CHD.

  Systolic Blood pressure (mm Hg)
< 147 147-166 ³167
(Serum cholesterol
mg/100 ml)		 # Men#Men with CHD # Men #Men with CHD # Men #Men with CHD
< 220 431 10 93 3 49 7
220 - 259347 1974 649 6
³ 260 18519 57 11 44 11

Consider the following groups:

  1. men with serum cholesterol under 220 mg/100 ml and systolic blood pressure under 147 mm Hg.;
  2. men with serum cholesterol 260 mg/100 ml and higher, and systolic blood pressure under 147 mm Hg;
  3. men with serum cholesterol under 220 mg/100 ml and systolic blood pressure 167 mm Hg and higher;
  4. men with serum choleterol 260 mg/100 ml and higher, and systolic blood pressure 167 mm Hg and higher.

Calculate the relative risk of coronary heart disease in relation to group (a) for group (c).

Relative risk: