Perception of risk

Molecules, Transport and Health · Health risks, evidence and treatment · note 3 of 7

Perception of riskSpec 1.17

In short

People’s perception of risk often differs from the actual risk. Dramatic, unfamiliar or involuntary risks tend to be overestimated, whereas familiar, voluntary or long-term risks, such as diet, smoking and inactivity, tend to be underestimated. Media coverage, personal experience, enjoyment and misunderstanding of statistics all influence perception.

The actual risk is the measured probability of harm, found from data. The perceived risk is what people think the risk is. The two often differ.

  • Overestimating: risks that are dramatic, rare and widely reported, or outside a person’s control (for example air travel).
  • Underestimating: risks from everyday lifestyle choices whose harm builds up slowly, such as a diet high in saturated fat, little exercise and smoking. People feel healthy now, and the harm is years away.
  • Reasons include media coverage, the experience of friends and family (a relative who smoked and lived to 90), the pleasure or convenience of the behaviour, believing the risk applies to others, and difficulty understanding statistics (for example confusing a large relative increase with a large absolute risk).

These differences matter because people who underestimate the risk of heart disease from diet and inactivity are less likely to change their behaviour. Health education aims to present the evidence clearly so perceived risk is closer to actual risk.

Exam tip:

Use the wording 'overestimate' and 'underestimate' with a named lifestyle risk, and give a reason such as media coverage or the delay before harm appears.

Written and checked against the Edexcel International A Level Biology (YBI11) specification · Updated October 2026

Frequently asked questions

What is the difference between correlation and causation?

A correlation is a relationship between two variables, such as smoking and heart disease. Causation means one variable directly produces the change in the other. A correlation does not prove causation, as a third (confounding) variable could be responsible, so extra evidence such as a mechanism is needed.

What is the difference between HDL and LDL cholesterol?

LDL carries cholesterol from the liver to the body tissues, and a high level raises the risk of atherosclerosis. HDL carries cholesterol from the tissues back to the liver, so a high HDL level is protective. A high LDL with a low HDL is the highest-risk combination.

How do you calculate BMI and waist-to-hip ratio?

BMI is body mass in kilograms divided by height in metres squared. Waist-to-hip ratio is waist circumference divided by hip circumference. Both indicate obesity, but BMI does not separate muscle from fat, while waist-to-hip ratio shows how much fat is stored around the abdomen.

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