# How to Control Which Categories Are Used When Computing Percentages and Averages on Tables

The categories used when computing statistics on tables are controlled via Value Attributes (see the example below). These can be edited in a variety of ways, including by:

- Right-clicking on the blue or brown row/column name on the table and selecting
**Values**. - Pressing the
`...`button in the Variables and Questions tab. - Right-clicking on a category that you wish to exclude from a category and selecting
**Remove**. - Automatically when using Set Question.
- Via QScript.

Individual categories are included or excluded as follows:

- If a category in the
**Missing Data**column, it will then be excluded from all calculations. (Note that if you can also see a**Missing Data**row, this refers to observations that are marked as missing values in the original data file.) - If a category has its
**Value**shown as`NaN`, it will be excluded from all numeric calculations (e.g., Average, Median), but will be included when computing percentages. Note that you will only see the**Value**column on data that can be represented numerically (e.g., it will not appear for Pick Any questions). - If it is a Date question, there is a completely different set of options (see Setting Time Periods for Date Questions).
- If you have Pick Any or Pick Any - Grid questions, there is a column called
**Count This Value**, which dictates the numerator when computing percentages. In the example below, for example, there are six unique categories in the data file:`Like`,`Love`,`Neither like nor dislike`,`Hate`,`Dislike`and`Missing data`, and the settings shown tell us that:- Anybody with
`Missing data`is excluded from any calculations. - The analysis will count up the number of people that have selected either
`Like`or`Love`. That is, this number will be the numerator in any calculations of percentages (i.e., the bit that goes above the line in a fraction). - The base used in calculating percentages consists of everybody except those people that have
`Missing data`. Thus, this particular example will compute Top 2 Box percentages scores (i.e., the proportion of people that said`Like`or`Love`from amongst all those people that selected one of the five categories).

- Anybody with

## Excluding categories when computing percentages

### Pick One and Pick One - Multi questions

Right-click on the category you wish to exclude and select Remove. This causes the table to be recomputed with this category removed. You can see which categories have been removed by right-clicking on a category and selecting Values and looking/editing the selections in the **Missing Data** column.

Alternatively, to remove a category from the table without affecting the calculations on a table, you can right-click the category and select **Hide**. This removes the category label from the table but does not change any of the **Missing Data** selections.

To undo the removal of categories from a table you can right-click the table and select **Revert**, or select Values and make changes to the selections in the **Missing Data** column.

## Excluding categories from averages

### Number, Number - Multi, and Number - Grid questions, and Statistics - Right and Statistics - Below

In some cases you may wish to keep a category showing in the table but remove it's contribution to the **Average**, **Sum**, or other numerical statistics that are displayed in the **Statistics - Right** or **Statistics - Below**. For example, a rating scale question may include a **Don't Know** category, and you want to know about the number of respondents who have selected this category without those respondents contributing to the calculation of the average score for the question.

To achieve this, right-click on your table and select Values, and enter a value of `NaN` in the **Value** column for that category. `NaN` stands for *Not a number*, and this value will not be used in the calculation of the average.

The same method is used to change the way the **Average**, **Sum**, or other numeric statistics are calculated for tables showing Number, Number - Multi, and Number - Grid questions.