Missing values for string variables are handled similarily to those for numeric values. Unlike numeric values, blank fields in string variables are not designated as system missing. Rather, they are interpreted as a blank string.

Click the Variable View tab at the bottom of the Data Editor window.

Click the Missing Values cell for the sex variable.

Click the button in this cell to open the Missing Values dialog box.

Select Discrete Missing Values.

Type NR for the missing value.

Missing values for string variables are case sensitive. So, a value of nr is not treated as a missing value.

Click OK to save your changes and return to the Data Editor.

Now you can add a label for the missing value.

Select the Values cell in the sex row and click the button to open the Value Labels dialog box.

Type NR for the Value.

Type No Response for the Value Label.

Click Add to have this label added to your project.

Click OK to implement your changes and return to the Data Editor.