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What is the entropy formula used after normalization and what does h represent?

The entropy formula is ej=−h∑i=1mrijln⁡rije_j=-h\sum_{i=1}^{m}r_{ij}\ln r_{ij}. The constant hh is a scaling factor defined as 1/ln⁡(m)1/\ln(m), where mm is the number of alternatives, ensuring the entropy values are properly scaled.

Conditions

  • The decision matrix has already been normalized to produce rijr_{ij}.
  • The natural logarithm ln⁡\ln is used.
  • mm represents the total number of alternatives (rows).

Reasoning, step by step

  1. Multiply each normalized value rijr_{ij} by its natural logarithm ln⁡rij\ln r_{ij}.
  2. Sum these products down each column.
  3. Multiply the column sum by the negative scaling constant −h-h.
  4. The result is the entropy eje_j for that specific criterion.

Example

For the Price or Cost column, the sum of rijln⁡rijr_{ij}\ln r_{ij} is -1.59938. Multiplying this by −h-h (where h=0.621335h=0.621335) yields an entropy of 0.99375.

Common misconceptions

  • Using a base-10 logarithm instead of the natural logarithm ln⁡\ln.
  • Forgetting to multiply by the negative sign, which would result in negative entropy values.

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