Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

To illustrate the reasoning process using expression (9.9), let us consider the
following example.
Example 9.3: Consider the hypothesis space and the evidence space for a
medical diagnosis problem. The rules, representing the cause-effect
relationship between the evidence space and the hypothesis space, are also
given along with the conditional probabilities.
Determine the probable disease that the patient bears.
T CP
0.2 GM 0.5 F HBA R
0.3
T = Typhoid F = Fever
GM = German Measles R = Rash
CP = Chicken Pox HBA = High Body Ache
Hypothesis space Evidence Space
Fig. 9.2: The hypothesis and the evidence space for example 9.3.
Here,
P (T) = 0.2,
P (CP) = 0.5,
P (GM) = 0.3
where P (X) denotes the probability that a patient has disease X.
Set of Rules
Rule 1: IF symptoms are
F ( P (F / T) = 0.9),
HBA (P (HBA / T) = 0.6)
THEN the Patient hopefully bears T.
Rule 2: IF symptoms are
F ( P(F/ GM) = 0.8),
R ( P (R / GM) = 0.7),
HBA ( P (HBA / GM) = 0.8)
THEN the patient hopefully bears GM.