Skip to main content
U.S. flag

An official website of the United States government

Here’s how you know

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

HTTPS

Secure .gov websites use HTTPS
A lock (LockA locked padlock) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

    • Environmental Topics
    • Air
    • Bed Bugs
    • Chemicals and Toxics
    • Climate Change
    • Emergency Response
    • Environmental Information by Location
    • Environmental Justice
    • Greener Living
    • Health
    • Land, Waste, and Cleanup
    • Lead
    • Mold
    • Pesticides
    • Radon
    • Science Topics
    • Water Topics
    • A-Z Topic Index
    • Laws & Regulations
    • By Business Sector
    • By Topic
    • Compliance
    • Enforcement
    • Guidance
    • Laws and Executive Orders
    • Regulations
    • Report a Violation
    • Environmental Violations
    • Fraud, Waste or Abuse
    • About EPA
    • EPA Administrator
    • Organization Chart
    • Staff Directory
    • Planning, Budget, and Results
    • Jobs and Internships
    • Headquarters Offices
    • Regional Offices
    • Lab and Research Centers
Related Topics:
  • Managing the Quality of Environmental Information
Contact Us

Using Professional Judgment to Develop a Sampling Design

Using professional judgment does not mean you must take judgmental samples. Implementation of a judgmental sampling design should not be confused with the application of professional judgment (or the use of professional knowledge of the study site or process). Professional judgment should always be used to develop an efficient sampling design, whether that design is judgmental or probability-based. For more information on when to use judgmental sampling or a probabilistic sampling design, see Selecting a Sampling Design.

Merits of Judgmental vs. Probabilistic Sampling

Judgmental Sampling Probabilistic Sampling
Selection of samples based on 
professional judgment and prior information
Selection of samples has a random component and may incorporate professional judgment and prior information
Should only be used to take a few samples (making it less expensive) Needs an adequate number of samples to support performance objectives (making it more expensive)
Can be cost-effective with expert knowledge Can be cost-effective with expert knowledge
Cannot reliably evaluate precision of estimates – does not allow the level of confidence in the results to be accurately quantified Can evaluate precision of estimates – allows the level of confidence of the investigation to be accurately quantified
Personal judgment is used to interpret data relative to study objectives Statistical inference is used to draw inferences from the data to the entire area/process.
Results are biased Protects against bias
Easy to implement Can be complicated to implement both in selecting samples and performing computations
Useful for emergency situations that need immediate sampling Useful for situations where the level of confidence of the final result should be accurately quantified.
 
Contact Us to ask a question, provide feedback, or report a problem.
United States Environmental Protection Agency

Discover.

  • Accessibility
  • Budget & Performance
  • Contracting
  • EPA www Web Snapshot
  • Grants
  • No FEAR Act Data
  • Plain Writing
  • Privacy
  • Privacy and Security Notice

Connect.

  • Data.gov
  • Inspector General
  • Jobs
  • Newsroom
  • Open Government
  • Regulations.gov
  • Subscribe
  • USA.gov
  • White House

Ask.

  • Contact EPA
  • EPA Disclaimers
  • Hotlines
  • FOIA Requests
  • Frequent Questions

Follow.

Last updated on June 16, 2021