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1.3.5Unit 1: Lifestyle, Transport, Genes and Health

Designing Studies into the Effects of Risk Factors — IAL Edexcel Linear Revision Notes & Topical Questions

5 min read 4 parts Lesson 23 of 29 Unit quiz

📚 IAL Edexcel Linear Hub / Topical Revision
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Part 1 of 4Types of Study

1.3.5 Designing Studies into the Effects of Risk Factors
Cohort study
  • A group of people is followed over many years and the number developing disease is recorded for those with and without the risk factor.
Case-control study
  • People who already have the disease are compared with matched people without it, looking back at their past exposure to the risk factor.
Clinical trial
  • A treatment is tested on volunteers, ideally by randomly assigning them to treatment and control groups.
Animal and laboratory studies
  • These can show a mechanism but results cannot be applied directly to humans.

Part 2 of 4Features of a Good Study

Features of a Good Study
Sample
  • A large, randomly chosen sample represents the population and reduces bias.
Controls
  • A control group is treated identically except for the factor being tested, giving a fair comparison.
Placebo and blinding
  • A placebo looks the same as the real treatment,
    • and in a double-blind trial neither participants nor researchers know who has which.
Variables
  • Age, sex, diet and other factors should be matched across groups so that only one variable is tested.

Part 3 of 4Reliability, Validity and Ethics

1
Results must be repeatable if the study is repeated, which shows that they are reliable.
2
The study must test what it claims to test, with confounding variables controlled, so that the results are valid.
3
Bias should be avoided in the choice of participants and in the way data are collected and analysed.
4
Participants must give informed consent, be told about possible risks and be free to withdraw at any time.
5
Results should be published and reviewed by other scientists so that conclusions can be checked.

Part 4 of 4Exam Checklist & Tips

1.3.5 – Key Points for the Exam

  • Placebo A treatment with no active ingredient given to the control group.
  • Double blind A trial in which neither the participants nor the researchers know who receives the treatment.
  • Cohort study A study following a group over time to see who develops a disease.
  • Informed consent Agreement to take part after being told the aims, methods and risks.

Common Mistakes

  • Choosing volunteers from one place, such as a gym, which gives a biased sample.
  • Having no control group, so there is no baseline for comparison.
  • Confusing reliable (repeatable) with valid (testing the right thing).
  • Ignoring ethical issues such as consent and the right to withdraw.

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