10 Types of Study Bias

Patrick Kiger::

A patient fills in a questionnaire and sleep diary before undergoing a polysomnography at a sleep center in Switzerland. What are some biasess scientists need to be aware of when conducting studies? AMELIE-BENOIST /BSIP/Getty Images

Arrhythmia, an irregular rhythm of the heart, is common during and soon after a heart attack and can lead to early death. That’s why when anti-arrhythmia drugs became available in the early 1980s, they seemed like a major life-saving breakthrough [source: Freedman].

The problem, though, was that although small-scale trials showed that the drugs stopped arrhythmia, the drugs didn’t actually save lives. Instead, as larger-scale studies showed, patients who received such treatments were one-third less likely to survive. Researchers had focused on stopping arrhythmia as a measure of effectiveness rather than on the problem that they were trying to solve, which was preventing deaths [sources: Freedman, Hampton].