21.4 Plastic (1st Part)
Which conclusions can be drawn from the - R chart? For this, using all default options, choose:
Stat > Control Charts > Variables Charts for Subgroups > Xbar–R. All observations for a chart are in one column: Length. Subgroup sizes: 4.
The process is clearly out of control. The R chart shows only one point outside the control limits (the rest does not seem to indicate signs of special causes).
The graph of the sample shows a nonrandom behaviour. During the first hours of the second day (around sample 10), there is a clear increase in the length ...