Differences

This shows you the differences between two versions of the page.

--- public:t-622-arti-14-1:lab_5_-_bayesian_networks [2014/03/04 10:22] – created stephan
+++ public:t-622-arti-14-1:lab_5_-_bayesian_networks [2024/04/29 13:33] (current) – external edit 127.0.0.1
@@ Line 10: / Line 10: @@
   * http://www.cs.cmu.edu/~javabayes/ (a slightly older Java applet)
-The following laws of probabilities might be helpful:
+==== Short explanation on how to use the first tool ====
+The application has two tabs "Create" and "Solve". In "Create" you can create and modify a Bayesian network, in "Solve" you can compute arbitrary probabilities using the network.
+Suppose you have a network with nodes A and B, where B depends on A.
+To create the network, you need to:
+  * create two nodes and give them the names A and B;
+  * create an arc pointing from A to B;
+  * modify the probability tables of both nodes and set the probabilities <latex>$P(A)$</latex>, <latex>$P(B|A)$</latex>, <latex>$P(B|\neg A)$</latex>.
+Suppose you want to compute <latex>$P(\neg A|\neg B)$</latex>, that is, you want to know the probability for A being false after having observed B being false. Then you need to:
+  * Go to the "Solve" tab;
+  * click on "Make Observation", then on node B and select "F" for false;
+  * click on "Query" and then on node A (select Brief query mode if asked).
+  * You should now see the probabilities for <latex>$P(A)$</latex> and <latex>$P(\neg A)$</latex> under the condition that B = false.
+==== Laws of Probabilities ====
+The following laws of probabilities might be helpful for developing formulas:
   * <latex>$P(\neg A) = 1 - P(A)$</latex>
   * Bayes Law: <latex>$P(A \land B) = P(A|B) * P(B)$</latex>