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SPSS® 12.0 Command Syntax Reference

SPSS® 12.0 Command Syntax Reference

SPSS® 12.0 Command Syntax Reference

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1514 SPCHART<br />

Figure 7 NP chart<br />

Data Organization<br />

Data for p and np charts can be organized in two ways: each case is a unit or each case is a<br />

subgroup.<br />

• Each case is a unit with a conformity status variable and a subgroup identifier. Cases are<br />

assigned to a category by the value of the subgroup identifier. Table 3 is an example of<br />

this type of data organization. The data do not have to be sorted. A BY variable (the<br />

subgroup identifier) is required to sort and aggregate data and label the category axis.<br />

• Each case is a subgroup. One variable contains the total number of items within a<br />

subgroup and one variable contains the total number of nonconforming or defective items<br />

in the subgroup. The subgroup identifier is optional. If specified, it is used for labeling<br />

purposes. Table 4 is an example of this type of data organization. The data are the same<br />

as used in Table 3.<br />

Table 3 Each case is a unit for p and np charts<br />

Subgroup Outcome<br />

January Cured<br />

January Cured<br />

January Cured<br />

January Relapse<br />

February Relapse<br />

February Cured<br />

February Relapse<br />

February Relapse<br />

... ...

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