Score

Proxy

Empirical

Method

Validation

4

An exact measure of the desired quantity

Controlled experiments and large sample direct mmts

Best available practice in well established discipline

Compared with independent mmts of the same variable over long domain

3

Good fit or measure

Historical/field data uncontrolled experiments small sample direct mmts

Reliable method common within est. discipline Best available practice in immature discipline

Compared with independent mmts of closely related variable over shorter period

2

Well correlated but not measuring the same thing

Modelled/derived data Indirect mmts

Acceptable method but limited consensus on reliability

Measurements not independent proxy variable limited domain

1

Weak correlation but commonalities in measure

Educated guesses indirect approx. rule of thumb est.

Preliminary methods unknown reliability

Weak and very indirect validation

0

Not correlated and not clearly related

crude speculation

No discernible rigour

No validation performed