non-response bias

Examples of non-response bias in the following topics:

• The Problems with Polls

  • Problems with polls typically stem either from issues with the methodology that bias the sample or the responses that cause the bias.
  • Since some people do not answer calls from strangers or refuse to answer the poll, poll samples may not be representative samples from a population due to a non-response bias.
  • In these cases, bias introduces new errors, in addition to errors caused by sample size.
  • Surveys may be affected by response bias, where the answers given by respondents do not reflect their true beliefs.
  • In statistics, self-selection bias arises in any situation in which individuals select themselves into a group, causing a biased sample with non-probability sampling.

• Telephone Surveys

  • As some people do not answer calls from strangers, or may refuse to answer the poll, poll samples are not always representative samples from a population due to what is known as non-response bias.
  • However, if those who do not answer have different opinions, then the results have bias.
  • In terms of election polls, studies suggest that bias effects are small, but each polling firm has its own techniques for adjusting weights to minimize selection bias.
  • Undercoverage is a highly prevalent source of bias.
  • In addition, if the pollsters only conduct calls between 9:00 a.m and 5:00 p.m, Monday through Friday, they are likely to miss a huge portion of the working population—those who may have very different opinions than the non-working population.

• Sampling from a population

  • This introduces bias into a sample.
  • The act of taking a simple random sample helps minimize bias, however, bias can crop up in other ways.
  • Even when people are picked at random, e.g. for surveys, caution must be exercised if the non-response is high.
  • This non-response bias can skew results.
  • Due to the possibility of non-response, surveys studies may only reach a certain group within the population.

• Biases in Experimental Design: Validity, Reliability, and Other Issues

  • Sampling bias occurs when the sample participating in the study is not representative of the general population.
  • Response bias (also known as "self-selection bias") occurs when only certain types of people respond to a survey or study.
  • Thus, the responses collected are biased and not representative of the general population of interest.
  • Many of the admittedly "non-scientific" polls taken on television or websites suffer from response bias.
  • A response bias can also result when the non-random component occurs after the potential subject has enlisted in the experiment.

• Media Bias

  • Media bias is the bias of journalists and news producers in the selection of events and stories that are reported, and how they are covered.
  • Media bias is the bias of journalists and news producers within the mass media, concerning the selection of events and stories that are reported, and how they are covered.
  • The term "media bias" implies a pervasive or widespread bias contravening the standards of journalism, rather than the perspective of an individual journalist or article.
  • The most commonly discussed forms of bias occur when the media support or attack a particular political party, candidate, or ideology; however, other common forms of bias exist, including advertising bias, corporate bias, mainstream bias, sensationalism, and concision bias.
  • However, the person organizing the report still has the responsibility to choose people who really represent the breadth of opinion, to ask them non-prejudicial questions, and to edit or arbitrate their comments fairly.

• How Well Do Probability Methods Work?

  • Failure to use probability sampling may result in bias or systematic errors in the way the sample represents the population.
  • This is especially true of voluntary response samples--in which the respondents choose themselves if they want to be part of a survey-- and convenience samples--in which individuals easiest to reach are chosen.
  • A third example of bias is called response bias.
  • Careful training of pollsters can greatly reduce response bias.
  • Finally, another source of bias can come in the wording of questions.

• Mass Media and Technology

  • Media bias refers the bias of journalists and news producers within the mass media.
  • The term "media bias" implies a pervasive or widespread bias contravening the standards of journalism, rather than the perspective of an individual journalist or article.
  • The direction and degree of media bias in various countries is widely disputed .
  • However, the person organizing the report still has the responsibility to choose people who really represent the breadth of opinion, to ask them non-prejudicial questions, and to edit their comments fairly.
  • The apparent bias of media is not always specifically political in nature.

• Memory Distortions and Biases

  • Another pattern for extra-list intrusions would be an acoustic similarity pattern, which states that targets that have a similar sound to non-targets may be replaced with those non-targets in recall.
  • There are many identified types of bias that influence people's memories.
  • Hindsight bias is the "I knew it all along!"
  • When remembering an event, individuals will often perceive themselves as being responsible for desirable outcomes, but not responsible for undesirable ones.
  • This is known as the self-serving bias.

• Sampling Bias

  • This section discusses various types of sampling biases including self-selection bias and survivorship bias.
  • Many of the admittedly "non-scientific" polls taken on television or web sites suffer greatly from self-selection bias.
  • A self-selection bias can result when the non-random component occurs after the potential subject has enlisted in the experiment.
  • Survivorship bias occurs when the observations recorded at the end of the investigation are a non-random set of those present at the beginning of the investigation.
  • Therefore, there is a bias toward selecting better-performing funds.

• Culture Bias

  • Bias is the state at which we all exist; that is, a non-neutral state of inclination, predilection, and prejudice.
  • Remember, bias doesn't necessarily mean exclusion, so bias can mean a preference for one culture over another.
  • Cultural bias exists in two forms when speaking in public.
  • There's the cultural bias you bring to the podium.
  • To overcome cultural bias, take a step back from your speech.