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Know the Science: 9 Questions To Help You Make Sense of Health Research

3. How large was the study?

Studies with large numbers of people generally get results that are more reliable than studies with small pools of participants. Larger studies can increase the accuracy of the study findings and reduce the probability that any effect observed in the study was due to chance. Too few participants may make the entire study a failure—it may only produce inconclusive results. Statisticians and scientists have tools to figure out how many volunteers are needed for a clinical study to be meaningful.

Study tests new treatment in 50 people

People receiving the treatment feel much better, but the researchers may not be sure other people will benefit

Statistical tests can’t tell whether this effect is real or due to chance

Study tests new treatment in 500 people

People receiving the treatment feel much better

Statistical tests indicate that the effect is real

In general, a large study with many volunteers may be able to produce conclusive results when a small study may not.