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Bias in an experiment refers to any factor that can influence the result of an experiment, such as participants knowing which group they belong to or the researcher favoring their focus on one of the groups. This bias can be done intentionally or unintentionally. Some of these factors will be described.
Selection bias refers to making some intervention when selecting the treatment and control groups. This bias can be avoided by randomly selecting the control and treatment groups to produce two similar groups.
The random selection can be performed through various methods ranging from flipping a coin or rolling a die to using a computer program to place members in each group.
It is caused when individuals know which group they belong to or if the researcher favors their focuses on one group more than the other. Doing that can cause the participants to change their responses or behaviors. From the point of view of the researcher, their expectations about the study results cause this bias. This factor can be avoided by using a blinding and a placebo.
| Solution | Description |
|---|---|
| Placebo | A fake treatment that is given to the control group, but it is harmless. An example would be receiving a sugar pill rather than prescription medication. |
| Blinding | This refers to preventing the groups or the researcher from knowing which one is the control and the treatment group. |
To make valid conclusions from an experiment, researchers must avoid any factor that can cause bias. Besides the given cases, many other factors that can cause bias, such as making errors in data collection.