Biases are systematic errors in the design or reporting of medical studies that produce a false pattern of differences between observed and actual results. Biases skew the actual effect of a treatment or medication.
Deeper dive
There’s a long list of biases that can occur in research, but some of the ones reporters should particularly look for include: Selection bias, or key baseline differences between groups that are to be compared; Attrition biases, or between-group differences who leaves a study; Performance biases, or differences in the care that is provided between two groups, or differences in exposures; and Reporting biases, or differences between reported and unreported findings.
For some examples, see “Don’t fudge the facts on chocolate studies.”