# Summary

- The Individual & Moving Range Chart is basically a variation on
the Mean & Range Chart.
- It is used in situations where data is being sought on a collection
of separate activities (eg. a project made up of several separate
events) or when the data is only available in a single measurement
or at irregular or infrequent times (eg. daily temperature, weekly
return, etc).
- The moving range is calculated by treating each successive pair of
X values as a subgroup of size 2 and calculating the difference
between the higher value and the lower one.
- Because each moving range is calculated using two X values, the
first mR is calculated only once the second X measurement has been
recorded. This means that the number of X values will always be one
more than the number of mR values.
- The calculated values are then recorded and plotted on the Chart in
the usual way.