Score = WQ x Qi + (WP - WP x log (Pi / Pbest) / log A)

Also written as (WQ x Qi) + (WP x (1 - log (Pi / Pbest) / log A))

WQ = Weighting quality

Qi = Quality of own registration

WP = Weighting price

LOG = The function that provides a logarithmic scale

Pi = Price own registration

Pbest = Price of the tender with the lowest price

A = Coefficient that the buyer must state in advance

In general, the formula is the sum of the quality score + the price score

Quality Q

The quality score is achieved just like with most other formulas; WQ x Qi; that is, multiplying the weight of quality (WQ) by the score of the relevant quotation (Qi) is the quality score of quotation āiā.

In practice, WQ x Qi is the sum of multiple (partial) quality criteria and multiple partial scores of the tender i per (partial) quality criterion. So WQ1 x Q1i + WQ2 x Q2i + etc.

Price P

Each quotation receives a number of price points which is added to the Q points. The number of price points per quotation i is calculated on the basis of 1 - log (Pi / Pbest) / log A

Coefficient A

A is a value that must specify purchasing in advance. The number determines the number of times the lowest price which gets zero price points. If A is 2, then a quote that is twice as expensive as the quote with the lowest price will receive zero price points. For A, 1.5, 2 or 3 is chosen in practice. Note that if a quotation i is more than A x as expensive as the quotation with the lowest price, then the number of price points of quotation i becomes negative.

Pi = Pbest applies to the quotation with the lowest price

The number of P points is then 1 - log (Pi / Pbest) / log A = 1 - log 1 / A = 1 - 0 / A = 1 = 100% This offer therefore receives all price points, regardless of A.

Due to the logarithmic scale, the difference in P scores of two offers is not dependent on the lowest price (Pbest). If the lowest price changes, the mutual ranking of the other offers remains unchanged. This is the idea why this formula was created.

## The Log Formula

Modified on: Tue, 17 Sep, 2019 at 2:47 PM

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