Type II error
Citation, DOI & article data
Type II errors (beta errors, β) occur when we accept that there is no difference between two experimental groups, when in fact, there is a difference.
The p-value does not give a direct indication of the likelihood of a type II error; if the p-value is >0.05, this does not necessarily mean that the two experimental groups are similar. This would only be true if the study is powered to a size to detect a difference if it were present 2.
By convention, we try to keep β = 0.15-0.20
Factors that affect the β:
- 1. Blackmore CC. The challenge of clinical radiology research. AJR Am J Roentgenol. 2001;176 (2): 327-31. doi:10.2214/ajr.176.2.1760327 - Pubmed citation
- 2. Altman DG. Practical Statistics for Medical Research (Chapman & Hall/CRC Texts in Statistical Science). Chapman and Hall/CRC. ISBN:0412276305. Read it at Google Books - Find it at Amazon
- 3. Trout AT, Kaufmann TJ, Kallmes DF. No significant difference . Says who?. AJNR Am J Neuroradiol. 2007;28 (2): 195-7. Pubmed citation