Types of Error
Type I error or alpha error
- A type I error or alpha error is when the the null hypothesis is rejected when it is true.
- The probability of committing a type I error is called the "level of significance" for a test and is often referred to as the alpha.
Type II error or beta error
- A type II error or beta error is when the null hypothesis is accepted when it is false.
Table 1: A diagram to illustrate the conditions when various types of error occur.
|
If H0 is true |
If H0 is false |
| If H0 is rejected |
Type I error
False Positive |
No error
True Positive |
| If H0 is not rejected |
No error
True Negative |
Type II error
False Negative |
Also See:
Chapter 10 - More on the Testing of Hypotheses pages 174 in:
-
Phillips, J. L. 2000. How to think about statistics. W. H. Freeman and Co. New York. 202 pp. ISBN 0-7167-3654-3
Chapter 6 - Introduction to statistical Hypothesis Testing pages 82-83 in:
-
Zar, J. H. 2007. Biostatistical Analysis. Prentice-Hall, Inc. Englewood
Cliffs, New Jersey. 718 pp.
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