Bias

Biases in research studies are systematic errors that favor or oppose a research hypothesis.

Bias may occur intentionally or unintentionally during the data collection, analysis, interpretation, or publication.

Of the several types of bias, a few common ones are included here.

Sampling bias can occur when samples are non-randomly drawn from the population, which is not an ideal representative of the entire population—for example, predicting the outcome of an election based on survey responses collected from only members of one political party and not of the whole electorate. 

Observer bias or research bias can occur when a researcher's preconceived notions, expectations, or incomplete knowledge influences the results and their interpretation.

Measurement bias occurs when poorly calibrated measuring instruments are used in the experiment.

Publication bias is observed when the research studies that report statistically significant positive findings are more likely to be published than the ones reporting negative results.

In the case of funding bias, researchers may skew the data to show outcomes favoring the funding body.