A filter defines one or more conditions: for example, that the respondent's gender must be male and age must be over 45. Regardless of how you define your filter, internally the conditions are expressed as a conditional expression (for example, "gender = {male} And age > 45"). A conditional expression returns a value of true or false for each case.

When you populate a table that has a filter on it, UNICOM Intelligence Reporter - Survey Tabulation applies the expression to each case. If the result is true, the case is selected and included in the table. This is sometimes called "passing the filter". If the result is false, the case is not selected and is excluded from the table.

In a simple filter, such as the one described above, it is quite easy to see which cases pass the filter. In more complicated filters it is not always so obvious. For example in a filter that defines certain categories that are to be excluded, only cases that are not in those categories pass the filter.