Probability Distribution

{
  "id": "MLC-T-ENV-022216",
  "term": "Probability Distribution",
  "field": "Environment",
  "definition": "1. A distribution of a variable that expresses the probability that particular attributes or ranges of attributes will be, or have been observed.\n\n2. A mathematical description of the relative probabilities of all possible outcomes of a measurement.\n\n3. Portrays the relative likelihood that a range of values is the true value of a treatment effect. This distribution often appears in the form of a bell-shaped curve. An estimate of the most likely true value of the treatment effect is the value at the highest point of the distribution. The area under the curve between any two points along the range gives the probability that the true value of the treatment effect lies between those two points. Thus, a probability distribution can be used to determine an interval that has a designated probability (e.g., 95%) of including the true value of the treatment effect.\n\n4. The probability distribution of a discrete random variable is a list of probabilities associated with each of its possible values. It is also sometimes called the probability function or the probability mass function. [STEPS 1997]\n\n5. The mathematical description of a function that associates probabilities with specified intervals or values for a random variable. A probability distribution can be displayed in a graph (e.g., PDF or CDF), summarized in a table that gives the distribution name and parameters, or expressed as a mathematical equation. In PRA, the process of selecting or fitting a distribution that characterizes variability or uncertainty can also be referred to as applying a probability model to characterize variability or uncertainty. In this guidance, the probability model is considered to be one source of model uncertainty.\n\n6. A function that for each possible value of a discrete random variable takes on the probability of that value occurring, or a curve which specifies by means of the area under the curve over an interval the probability that a continuous random variable falls within the interval (the probability density function). [FAO/WHO 2003b]\n\n7. Portrays the relative likelihood that a range of values is the true value of a treatment effect. This distribution often appears in the form of a bell-shaped curve. An estimate of the most likely true value of the treatment effect is the value at the highest point of the distribution. The area under the curve between any two points along the range gives the probability that the true value of the treatment effect lies between those two points. Thus, a probability distribution can be used to determine an interval that has a designated probability (e.g., 95%) of including the true value of the treatment effect. [NLM/NICHSR 2004][MRA Thesaurus]\n\n8. Describe the range of values that certain variables might take within a population and estimate the relative likelihood (probability) that any of those values might occur in the given population. [U.S. EPA Risk Assessment Guidance for Superfund (RAGS) Volume III - Part A (https://www.epa.gov/risk/risk-assessment-guidance-superfund-rags-volume-iii-part)]\n\n9. Describe the range of values that certain variables might take within a population and estimate the relative likelihood (probability) that any of those values might occur in the given population.",
  "subject": "Science and research",
  "references": [
    "Program Evaluation Glossary",
    "Benchmark Dose Software (BMDS) Glossary of Terms",
    "NLM/NICHSR 2004",
    "Thesaurus of Terms Used in Microbial Risk Assessment",
    "EPA RAGS Volume 3 Part A ~ Process for Conducting Probabilistic Risk Assessment Appendix B at http://www.epa.gov/oswer/riskassessment/rags3adt/pdf/appendixb.pdf",
    "EPA ExpoBox Terminology",
    "U.S. EPA Risk Assessment Guidance for Superfund (RAGS) Volume III - Part A (https://www.epa.gov/risk/risk-assessment-guidance-superfund-rags-volume-iii-part)"
  ],
  "url": "https://mlchart.com/terminology/environment/probability-distribution/"
}