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Merck
Manual
Consumer Version
The trusted provider of medical information since 1899
ENGLISH
ESPAÑOL (SPANISH)
Other Languages
Search
Search
A-Z
VIEW PROFESSIONAL VERSION
HOME
HEALTH TOPICS
Common Health Topics
Blood Disorders
Bone, Joint, and Muscle Disorders
Brain, Spinal Cord, and Nerve Disorders
Cancer
Children's Health Issues
Digestive Disorders
Disorders of Nutrition
Drugs
Ear, Nose, and Throat Disorders
Eye Disorders
Fundamentals
Heart and Blood Vessel Disorders
Hormonal and Metabolic Disorders
Immune Disorders
Infections
Injuries and Poisoning
Kidney and Urinary Tract Disorders
Liver and Gallbladder Disorders
Lung and Airway Disorders
Men's Health Issues
Mental Health Disorders
Mouth and Dental Disorders
Older People’s Health Issues
Skin Disorders
Special Subjects
Women's Health Issues
Resources
Videos
Figures
Images
Quizzes
Common Medical Tests
View All Resources
SYMPTOMS
General
Abdomen & Digestive
Bleeding
Brain & Nervous System
Chest & Respiratory
Children's Symptoms
Eye
Genital & Urinary
ALL SYMPTOMS >
EMERGENCIES
Cardiac Arrest
Choking
ALL EMERGENCIES >
DRUG INFO
Drug Information, Search
Drugs by Name, Generic and Brand
Natural Products, Search
Drug Interactions
Pill Identifier
Commonly searched drugs
Aspirin
Metformin
Warfarin
Tramadol
Lactulose
Ranitidine (Withdrawn from US Market)
RESOURCES
Abbreviations
Audio
3D Models
Common Medical Tests
Figures
First Aid
Images
Infographics
Lab Test
Medical Terms
The One-Page Manual of Health
Pronunciations
Quizzes
Self-Assessment Tools
Tables
Videos
Weights & Measures
Podcasts
NEWS
Seniors With Depression Show Resilience in Face of Pandemic
Some Fall Allergy Symptoms Could Have You Thinking COVID
AHA News: As the Coronavirus Upends Schools, Experts Say Don't Forget the Arts
Are Opioids Prescribed Too Freely as Patients Are Moved to Nursing Homes?
View All News >
View All News >
ABOUT
Overview
History
Editors and the Editorial Process
Publishing and Production Staff
Editorial Board
Contributors
Reviewers
Content Providers
Global Medical Knowledge 2020
FAQ
Contact Us
Health Topics & Chapters
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
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The Science of Medicine and Clinical Trials
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The Science of Medicine and Clinical Trials
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The Science of Medicine
Treatment and recovery: Cause and effect?
How Doctors Try to Learn What Works
Sample size
Control groups
Time frame
Comparing apples to apples
Eliminating other factors
Choosing a clinical trial design
What Participants Need to Know About Clinical Trials
Types of clinical trials
The Clinical Trial Participation Experience
Finding a clinical trial
While in the clinical trial
Risks and Benefits of Participation in Clinical Trials
Risks of participation in clinical trials
Benefits of participation in clinical trials
Problems and Safeguards in Clinical Trials
More Information