What is a Type I Error?

A type I error is a type of error that occurs in statistical hypothesis testing in which a true null hypothesis is rejected. When a null hypothesis which is actually true is rejected when it should not be, a type I error has occurred. In statistical hypothesis testing, a null hypothesis is often established before the test. A type I is also called a false positive finding or conclusion, it is an error of rejecting a true null hypothesis that should otherwise not be rejected. This error thereby accepts an alternative hypothesis when the results of the test are still subject to probability.

Back to: RESEARCH, ANALYSIS, & DECISION SCIENCE

How does a Type I Error Occur? 

A type I error often occurs when there is an absence of a relationship between the item being tested, the stimuli applied and the outcome. A Type I error is called a false positive finding or conclusion that occurs when the outcome of a hypothesis test is caused by something outside of the stimuli or caused by chance. When there is no connection between the tets subject and the stimuli, a false positive is given. When this happens, there is a rejection of a null hypothesis which is actually true and meant to be accepted.

Example of a Type I Error

A type I error can occur in diverse fields and various testings, for instance, if a new drug is being tested in a medical laboratory, a type I error when the drug is taken to be an effective remedy for a particular illness when it is actually not. In the legal field, a type I error occurs when an innocent person is sent to jail when he should not have been. One common attribute of type I errors is that something which should not have been rejected is rejected or something which should not have been accepted is accepted.