dealing with uncertainty the need to deal with uncertainty arose in “expert systems” code...

6

Dealing with Uncertainty The need to deal with uncertainty arose in “expert systems” Code expertise into a computer system Example: Medical diagnosis: MYCIN Equipment failure diagnosis in a factory Sample from MYCIN: IF The infection is primary-bacteremia AND The site of the culture is one of the sterile sites AND The suspected portal of entry is the gastrointestinal tract THEN There is suggestive evidence (70%) that the infection is bacteroid Expert systems often have long chains IF X THEN Y … IF Y THEN Z … IF Z THEN W … If uncertainty is not handled correctly, errors build up, wrong diagnosis Also, there may be dependencies, e.g. X and Y depend on each other Leads to more errors… Need a proper way to deal with uncertainty

Upload: rosalind-adams

Post on 18-Dec-2015

212 views

Category:

Documents

0 download

Report

Download

Embed Size (px):

TRANSCRIPT

Page 1: Dealing with Uncertainty The need to deal with uncertainty arose in “expert systems” Code expertise into a computer system Example: Medical diagnosis:

Dealing with Uncertainty The need to deal with uncertainty arose in “expert systems”

Code expertise into a computer systemExample: Medical diagnosis: MYCIN Equipment failure diagnosis in a factory

Sample from MYCIN: IF

The infection is primary-bacteremia AND The site of the culture is one of the sterile sites AND The suspected portal of entry is the gastrointestinal tract

THEN There is suggestive evidence (70%) that the infection is bacteroid

Expert systems often have long chains IF X THEN Y … IF Y THEN Z … IF Z THEN W … If uncertainty is not handled correctly, errors build up, wrong diagnosis Also, there may be dependencies, e.g. X and Y depend on each other Leads to more errors…

Need a proper way to deal with uncertainty

Page 2: Dealing with Uncertainty The need to deal with uncertainty arose in “expert systems” Code expertise into a computer system Example: Medical diagnosis:

How do Humans Deal with Uncertainty? Not very well…

Consider a form of cancer which afflicts 0.8% of people (rare) A lab has a test to detect the cancer The test has a 98% chance to give an accurate result Mr. Bloggs goes for the test

The result comes back positive i.e. the test says he has cancer

What is the chance that he has the cancer? 28%

Afflicts experts too Studies have shown: human experts thinking of likelihoods do not reason

like mathematical probability

Page 3: Dealing with Uncertainty The need to deal with uncertainty arose in “expert systems” Code expertise into a computer system Example: Medical diagnosis:

A

B C

D E

Increased total serum count

Metastatic cancer

Brain Tumour

Severe headachesComa

No Link

Page 4: Dealing with Uncertainty The need to deal with uncertainty arose in “expert systems” Code expertise into a computer system Example: Medical diagnosis:

A

B C

D E

Increased total serum count

Metastatic cancer

Brain Tumour

Severe headachesComa

Serum count

Brain tumour

Coma

Yes Yes 95%

Yes No 94%

No Yes 29%

No No 0.1%

Brain tumour

headache

Yes 70%

No 1%

… …

… …

… …

… …

… …

… …

… …

… …

… …

Page 5: Dealing with Uncertainty The need to deal with uncertainty arose in “expert systems” Code expertise into a computer system Example: Medical diagnosis:

Inference in Belief Networks Questions for a belief network:

Diagnosis Work backwards from some evidence to a hypothesis

Causality Work forwards from some hypothesis to likely evidence Test a hypothesis, find likely symptoms

In general – mixed mode Give values for some evidence variables Ask about values of others

No other approach handles all these modes

Reasoning can take some time Need to be careful to design network Local structure: few connections

Page 6: Dealing with Uncertainty The need to deal with uncertainty arose in “expert systems” Code expertise into a computer system Example: Medical diagnosis:

How Good are Belief Networks? Relieves you from coding all possible dependencies

How many possibilities if full network?

Tools are available Build network graphically System handles mathematical probabilities

Case study: Pathfinder a medical expert system

Assists pathologists with diagnosis of lymph-node diseases Pathfinder is a pun

User enters initial findings Pathfinder lists possible diseases User can

Enter more findings Ask pathfinder which findings would narrow possibilities

Pathfinder refines the diagnosis Pathfinder version based on Belief Networks performs significantly better

than human pathologists

Dealing With Statistical Uncertainty

Chapter 10 Dealing with Uncertainty

Challenges of dealing with uncertainty

Dealing with Uncertainty

Dealing with climatic uncertainty - Remediation … · Dealing with climatic uncertainty ... Acknowledgement of the source of both the ... fed through the plates to encourage rusting

SKIM presentation PBIRG 2012: dealing with uncertainty in forecasting

Dealing with uncertainty in emergency assessment · Dealing with uncertainty in emergency assessment: ... +49 (0) 631 205 5014 ... This paper benefited from insightful comments of

Dealing with uncertainty in emerging assessments

Chapter 3 Dealing with Demand Uncertainty us- ing … · Chapter 3 Dealing with Demand Uncertainty us-ing Sample Average Approximation ... parallelization in a computational grid

Tools for Dealing with Uncertainty, Ambiguity, and Paradox

DEALING WITH UNCERTAINTY IN INVENTORY OPTIMIZATION · 2016-07-15 · 148 DEALING WITH UNCERTAINTY IN INVENTORY OPTIMIZATION 6.2.7 Final Thoughts The analysis above only considers

Dealing with Uncertainty in Statics 1. Outline Uncertainty in statics Why consider uncertainty Basics of uncertainty Uncertainty analysis in statics Examples

Dealing with Valuation Uncertainty...Dealing with Valuation Uncertainty Greg Preston, Managing Director Preston Rowe Paterson. April 2020. Overview • The underlying value of all

Dealing with Estimation, Uncertainty, Risk, and Commitment

Corporate Finance Lecture 5. Topics covered Decision trees Decision trees Dealing with uncertainty Dealing with uncertainty –Sensitivity analysis –Senario

Robust workforce planning: dealing with uncertainty

DEALING WITH UNCERTAINTY IN SAFETY FUNCTION FAILURE …

Dealing with Uncertainty: Concepts and Tools · Dealing with Uncertainty: Concepts and Tools ... 2/17/2004. Decision Making Under Risk ... Slide 1 Author: Nathaniel Osgood

Dealing with uncertainty: from agile to antifragile

Tools for Dealing with Uncertainty, Ambiguity, and …perspegrity.com/papers/NCDD08_Uncertainty_Methods... · NCDD 2008 Reflective Tools for Dealing with Uncertainty Murray, Ross,

Dealing with uncertainty: A guide for DB trustees dealing

Paula Matuszek CSC 8520, Fall, 2005 Dealing with Uncertainty

DEALING WITH UNCERTAINTY - OMV MARINE DISCHARGE … · Stantec Dealing with Uncertainty - OMV Marine Discharge Consent Application July 2018 Status: Final Project No.: 80510334 Our

Dealing with Medical Uncertainty

SharedCanvas: Dealing with Uncertainty in Digital Facsimiles

CS 326A: Motion Planning Kynodynamic Planning + Dealing with Moving Obstacles + Dealing with Uncertainty + Dealing with Real-Time Issues

Section 3C Dealing with Uncertainty Pages 168-178

Evolutionary Computation in Games: Dealing With Uncertainty · • Uncertainty • Uncertainty in Games • Examples. Evolutionary Computation In Games •Objective functions-Player:

Organizational Strategies for Dealing with Uncertainty · 2010-07-20 · Dealing with Uncertainty David Cleden Author of: Managing Project Uncertainty. define terms what’s the problem?

‘Dealing With Risk and Uncertainty in Coastal Environments’ · ‘Dealing With Risk and Uncertainty in Coastal Environments’ A one-day workshop Cambridge, Wednesday 22nd March

DEALING WITH UNCERTAINTY IN ENGINEERING AND …

Dealing with uncertainty and risk in rock engineering design

Dealing with Uncertainty - Our Business World

Dealing with Uncertainty in Transportation and Distributioniieom.org/pujawan.pdf · Dealing with Uncertainty in Transportation and Distribution ... VMI Dysney & Towill ... • Shipment

Dealing with Valuation Uncertainty - Property Funds · 2020-04-30 · Dealing with Valuation Uncertainty Greg Preston, Managing Director Preston Rowe Paterson. April 2020. Overview