payment page
Bias is the distortion of results by a variable. Common types of bias include sampling bias, participant bias, and experimenter bias.
Sampling Bias
Sampling bias occurs when the sample studied in an experiment does not correctly represent the population the researcher wants to draw conclusions about.
Example: A psychologist wants to study the eating habits of a population of New Yorkers who have freckles and are between the ages of 18 and 45. She can’t possibly study all people with freckles in that age group, so she must study a sample of people with freckles. However, she can generalize her results to the whole population of people with freckles only if her sample is representative of the population. If her sample includes only white, dark-haired males who are college juniors, her results won’t generalize well to the entire population she’s studying. Her sample will reflect sampling bias.
Participant Bias
Research participants’ expectations can affect and change the participants’ behavior, resulting in participant bias. Such a bias can manifest itself in several ways:
A placebo effect is the effect on a participant receiving a fake drug or treatment. Placebo effects occur when participants believe they are getting a real drug or treatment even though they are not. A single-blind experiment is an experiment in which the participants don’t know whether they are receiving a real or fake drug or treatment. Single-blind experiments help to reduce placebo effects. It should be noted that the placebo effect is not limited to drug studies; it can happen in any research where participants’ expectations about an intervention influence outcomes.
The social desirability bias is the tendency of some research participants to describe themselves in socially approved ways. It can affect self-report data or information people give about themselves in surveys.
The demand characteristics bias occurs when participants alter their behavior based on their perceptions of the study’s purpose or what they believe the researcher expects from them. This bias often leads participants to behave in ways that align with perceived expectations, which can skew the results of the study.
Example: In a psychological experiment on stress, participants might exaggerate their stress levels if they think the researcher is looking for evidence of heightened anxiety. Researchers minimize demand characteristics by using techniques such as deception (when ethically appropriate) to obscure the true purpose of the study or by designing tasks that do not reveal the research hypothesis.
The Hawthorne effect occurs when participants change their behavior simply because they know they are being observed rather than as a result of the experimental conditions. This bias was first identified in workplace studies at the Hawthorne Works factory, where workers increased their productivity when they knew they were being monitored. The effect demonstrates how the awareness of observation can influence performance, regardless of other variables. Researchers can minimize the Hawthorne effect by conducting longer studies to allow participants to adapt to being observed or by using unobtrusive observation methods, provided these methods follow ethical guidelines.
The stereotype threat bias occurs when participants underperform or alter their behavior because they fear confirming a negative stereotype about their social group. This bias highlights how awareness of societal stereotypes can create additional stress or anxiety, influencing performance or decision-making. For instance, women taking a math test may score lower if they are reminded of the stereotype that men are better at math, even if their actual abilities or comparable. Researchers can reduce stereotype threat by avoiding group comparisons in the study setup and creating a supportive, neutral environment that minimizes the attention on stereotypes.
The response bias occurs when participants consistently respond in a patterned way that does not reflect their true thoughts, feelings, or behaviors. This bias can appear in forms such as extreme responding, where participants always select the highest or lowest options, or central tendency bias, where participants always choose “strongly agree” on a survey, regardless of the question’s content, either to save time or because they are unsure how to respond. Researchers can reduce response bias by designing balanced response scales that incorporate reverse-worded questions to identify patterns and encouraging participants to take their time and answer thoughtfully.
Experimenter Bias
Experimenter bias occurs when researchers’ preferences or expectations influence the outcome of their research. In these cases, researchers see what they want to see rather than what is actually there.
A method called the double-blind procedure can help experimenters prevent this bias from occurring. In a double-blind procedure, neither the experimenter nor the participant knows which participants come from the experimental group and which come from the control group.
