  Millions of measuring instruments are verified each year before being placed
on the markets worldwide. In the EU, such initial conformity assessments are
regulated by the Measuring Instruments Directive (MID). The MID modules F and
F1 on product verification allow for statistical acceptance sampling, whereby
only random subsets of instruments need to be inspected. This paper
re-interprets the acceptance sampling conditions formulated by the MID. The new
interpretation is contrasted with the one advanced in WELMEC guide 8.10, and
three advantages have become apparent. Firstly, an economic advantage of the
new interpretation is a producers' risk bounded from above, such that measuring
instruments with sufficient quality are accepted with a guaranteed probability
of no less than 95 %. Secondly, a conceptual advantage is that the new MID
interpretation fits into the well-known, formal framework of statistical
hypothesis testing. Thirdly, the new interpretation applies unambiguously to
finite-sized lots, even very small ones. We conclude that the new
interpretation is to be preferred and suggest re-formulating the statistical
sampling conditions in the MID. Re-interpreting the MID conditions implies that
currently available sampling plans are either not admissible or not optimal. We
derive a new acceptance sampling scheme and recommend its application.
