Data for c and u charts can be organized where
each case is a unit or where each case is a subgroup.
- If each case is a unit with a variable containing
the number of defects for that unit and a subgroup identifier, cases
are assigned to each subgroup by the value of the identifier. Table 1 is
an example of this type of data organization. Data do not have to
be sorted by subgroup. A
BY variable
(the subgroup identifier) is required to sort and aggregate data and
to label the category axis.
- If each case is a subgroup, one variable contains
the total number of units within the subgroup, and one variable contains
the total number of defects for all units within the subgroup. The
subgroup identifier is optional. When specified, the subgroup identifier
is used as category axis labels;
otherwise, the number 1 to the number of subgroups are used to label
the category axis. Table 2 is
an example of this method of data organization. The data are the same
as the data in Table 1.
Table 1. Each case
is a unit for c and u charts
| ID |
Subgroup |
Count |
| 1 |
January |
0 |
| 2 |
January |
2 |
| 3 |
January |
0 |
| 4 |
January |
0 |
| 5 |
February |
5 |
| 6 |
February |
1 |
| 7 |
February |
0 |
| 8 |
February |
0 |
| ... |
... |
... |
Table 2. Each case
is a subgroup for c and u charts
| Subgroup |
Relapses |
N |
| JANUARY |
1 |
4 |
| FEBRUARY |
3 |
4 |
| ... |
... |
... |