Question

A doctor is studying the relationship between blood pressure and heartbeat abnormalities in her patients. She tests a random sample of her patients and notes their blood pressures (high, low, or normal) and their heartbeats (regular or irregular). She discovers 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.

• Of those with normal blood pressure, one-eighth have an irregular heartbeat.

Determine the percentage of the patients that have

(a) a regular heartbeat and high blood pressure.

(b) a regular heartbeat and normal blood pressure.

(c) an irregular heartbeat and low blood pressure.

Answer 1

Consider 100 people.

Out of these,

• 14 have high blood pressure.
• 22 have low blood pressure.
• 64 have normal blood pressure.
• 15 have an irregular heartbeat. implies 85 have regular heartbeat.
• 5 people have both irregular heartbeat and high blood pressure implies 9 or 9% people have regular heartbeat and high blood pressure, this answers Part (a).
• 8 people have irregular heartbeat and normal blood pressure. This implies 56 or 56% people have a regular heartbeat and normal blood pressure, this answers part (b).
• 2 or 2% people have irregular heartbeat and low blood pressure, this answers part (c)