Probability Problem

  • A doctor is studying the relationship between blood pressure and heart beating abnormalities in her patients. She tests a random sample of her patients and notes their blood pressures (Low , Normal , High) and their heartbeats (regular or irregular). She finds that 14% have high blood pressure , 22% have low blood pressure , 15% have an irregular heartbeat. Of those with an irregular heartbeat (one - third) have high blood pressure and of those with normal blood pressure (one - eight) have an irregular heartbeat.
  • The proportion of patients with regular heartbeat and low blood pressure from this group is………………….
  • I didn't get the meaning of (one third) and (one - eight), I need the help as soon as possible please.


TS Contributor
15% have an irregular heartbeat, and of those patients with irregular heartbeat, 1 out of 3 has high blood pressure.

Acccordingly, X% have a normal blood pressure, and of those patients with normal blood pressure, 1 out of 8 has irregular heartbeat.

Suppose that the percentage are based on the examintation of n=100 patients. Then, n=15 have an irregular heartbeat, and of these 15 patients, 1/3 (n=...) have high blood presure.