. In a canning plant, dry powder is packed into cans with a nominal weight
of 2000 gm. Cans are filled at a 4-head filler fed by a hopper, with each
head filling about 25 cans every two minutes. The process is controlled by
a computer program which calculates very crude adjustments to fill-times
based on the filled weight recorded at a check weigher. Adjustments, once
made, are maintained for at least 5 cans, so that a subgroup of 5 cans is a
natural subgroup for studying the process. The automatic adjustment was
justified by the expectation that powder density will often change because
of the settling effects in the bins where it is stored prior to canning. To see
how the process was performing, weights were recorded for 5 successive cans
every two minutes for 60 minutes. These weights, expressed as deviations
from 1984 gm, are given in Table 1