  Correlations that cannot be reproduced with local variables certify the
generation of private randomness. Usually, the violation of a Bell inequality
is used to quantify the amount of randomness produced. Here, we show how
private randomness generated during a Bell test can be directly quantified from
the observed correlations, without the need to process these data into an
inequality. The frequency with which the different measurement settings are
used during the Bell test can also be taken into account. This improved
analysis turns out to be very relevant for Bell tests performed with a finite
collection efficiency. In particular, applying our technique to the data of a
recent experiment [Christensen et al., Phys. Rev. Lett. 111, 130406 (2013)], we
show that about twice as much randomness as previously reported can be
potentially extracted from this setup.
