  We comment on the so-called negative-result experiments (also known as null
measurements, interaction-free measurements, and so on) in quantum mechanics
(QM), in the light of the new general understanding of the quantum-measurement
processes, proposed recently. All experiments of this kind (null-measurements)
can be understood as improper measurements with an intentionally biased
detector set up, which introduces exclusion or selection of certain events. The
prediction on the state of a microscopic system under study based on a null
measurement, is sometimes dramatically described as ``wave-function collapse
without any microsystem-detector interactions". Though certainly correct, such
a prediction is just a consequence of the standard QM laws, not different from
the situation in the so-called state-preparation procedure. Another closely
related concept is the (first-class or) repeatable measurements. The
verification of the prediction made by a null-measurement requires eventually a
standard unbiased measurement involving the microsystem-macroscopic detector
interactions, which are nonadiabatic, irreversible processes of signal
amplification.
