Type II Error

{
  "id": "MLC-T-ENV-028922",
  "term": "Type II Error",
  "field": "Environment",
  "definition": "1. Acceptance of a false null hypothesis.\n\n2. False negative; the error made when the null hypothesis is accepted when in fact the alternative hypothesis is true. [EPA Definitions of Terms Relevant to PRA and References for Further Reading at http://www.epa.gov/oswer/riskassessment/rags3adt/pdf/appendixe.pdf]\n\n3. The probability of a type II (false-negative) error. In hypothesis testing, β is the probability of concluding incorrectly that an intervention is not effective when it has true effect. (1-β) is the power to detect an effect of an intervention if one truly exists. [NLM/NICHSR 2004]\n\n4. In a hypothesis test, a beta (or type II) error occurs when the null hypothesis, H₀, is not rejected when it is in fact false. For example, in a clinical trial of a new drug, the null hypothesis might be that the new drug is no better, on average, than the current drug; i.e., H₀: there is no difference between the two drugs on average. A type II error would occur if it was concluded that the two drugs produced the same effect, i.e., there is no difference between the two drugs on average, when in fact they produced different ones. A type II error is frequently due to sample sizes being too small. The probability of a type II error is generally unknown, but is symbolised by β and written P(Type II error) = β. A type II error can also be referred to as an error of the second kind. [STEPS 1997]\n\n5. False negative; the error made when the null hypothesis is accepted when in fact the alternative hypothesis is true.",
  "subject": "Ecosystems",
  "see_also": [
    "beta error",
    "False Negative"
  ],
  "references": [
    "Waste and Cleanup Risk Assessment Glossary",
    "NSTEPS Online Glossary of Terms",
    "Thesaurus of Terms Used in Microbial Risk Assessment",
    "N-STEPS Online Glossary of Terms"
  ],
  "url": "https://mlchart.com/terminology/environment/type-ii-error/"
}