Measuring Science (II) Morten Brendstrup-Hansen

No science without scientific publications Scientific publications are direct and tangible products of scientific activity Therefore, the idea of a measure of scientific performance based on publications is sound and straightforward

Peer review vs. bibliometric analysis Peer review may be accurate, but is time consuming and may easily be (suspect of being) biased The accuracy of a scholarly founded formal bibliometric analysis may be examined and its validity may be discussed A bibliometric analysis is based on publicly available (and easily collected) data

In bibliometrics, what should we count/calculate? Where do we find the data for bibliometric analyses?

Total number of papers Measures quantity, but does not take quality into account; does not give due weight to influence

Number of 'quality papers' e.g. defined as papers in ISI-journals Relies on the inclusion in a particular journal as a measure of quality instead of trying to assess the actual quality of the paper

Total number of citations Measures influence, but may be inflated by a small number of unrepresentative big hits

Number of citations per paper Punishes productivity

Number of papers with >x citations Combines publication data with citation data Thus rewards quality as well as quantity if a fair value of x is chosen, but different values of x need to be decided upon for different fields of research

h-index A scientist has the index h if h of his or her papers have at least h citations each - Hirsch JE (2005) PNAS 102(46): Nc Np h h

h-index A scientist has the index h if h of his or her papers have at least h citations each - Hirsch JE (2005) PNAS 102(46): Nc Np h h

g-index A set of papers has a g-index g if g is the highest rank such that the top g papers have, together, at least g 2 citations - Egghe L (2006) Scientometrics 69(1):

This is only the beginning More indices will probably be coined Indices should be validated e.g. by testing their predicative power

Software link Publish or Perish is a piece of software that calculates several bibliometric indices from Google Scholar data. It is provided free of charge at