Type I Error
The incorrect rejection of a true null hypothesis (a false positive).
What is Type I Error?
A Type I error occurs when a researcher concludes that there is a statistically significant effect, difference, or relationship when, in reality, none exists. It is the error of seeing a pattern where there is only random noise.
Why Type I Error Matters
Type I errors lead to false discoveries, which can result in wasted resources, ineffective treatments being approved, or invalid theories being accepted into the literature.
How to Interpret
The probability of making a Type I error is denoted by alpha (ฮฑ), which is directly controlled by the significance level chosen by the researcher (usually 0.05).
Example
A medical trial concludes that a new sugar pill cures headaches better than a placebo, purely due to a statistical fluke in the sample data.
Common Mistakes
- Failing to correct for multiple comparisons (like applying a Bonferroni correction), which drastically inflates the overall Type I error rate.