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This is drawn as an option to decision trees as the size of the tree grows too big. A decision table
takes the form of a table as shown below. The aims in preparing a decision table are; (1) To ensure
that all conditions and their associated actions are included, and; (2) To ensure that all rules are both
logical and clearly understood - with no ambiguity.
Decision table could be: (1) Limited condition/limited action or; (2) Extended condition/extended
A limited condition entry consists of a “Yes” or a “No” or is irrelevant (Y, N and – respectively). Also,
a limited action entry comprises one or more crosses in each column to indicate the action stub(s) or
otherwise a blank. The tables given are of this type. In any case, they are clearer to follow though
they may become numerous if many decisions are involved.
How to draw a decision table- Illustration:
An organization which operates solely by mail order uses the following procedure when an order is
received for a product.
“If the product is still in stock, the goods are shipped at once, the stock level checked, and an order
issued on suppliers if necessary. When the product is out of stock, it is ordered from the suppliers
unless an order has already been placed. Where the item has been discontinued, a substitute is