Question

What is bias? How can it influence the results of a statistical study?

Answer 1

Bias is the tendency of a measurement process to over- or under-estimate the value of a population parameter. In a survey sampling, for example, bias would be the tendency of a sample statistic to systematically over- or under-estimate a population parameter.

In simple words Bias is the ability of the human mind to impose judgements and meanings on people, things, and situations.

Bias is often introduced when a study is being designed, but can be introduced at any stage.

Various types of bias influence the results of statistical study differently.

For example :

when we are selecting sample or data wrong. Usually this means accidentally working with a specific subset of the audience instead of the whole, rendering sample unrepresentative of the whole population. There are many underlying reasons, but by far the most typical is collecting and working only with data that is easy to access.

For example we want to do a study on what proportion of the people in the country has access to clean water, for that we only survey a city which is in the urban area, so these results would have a bias as they sample is not fully representative of rural areas where the people are more likely to not have access to clean water.