Masks

Answer/Scale Masks

If you want to remove certain columns or rows from a table, you can apply an answer or scale mask. Scale masks are only available for grids.

To specify an answer mask, click the … button beside the “Answer Mask” property in the property sheet for the variable you want to mask .

Figure 1 - Setting the Answer Mask

A Select Answers window opens . Here you must find and select the answers you wish to mask. Above the "Selected items" list is a drop-down in which you specify whether the elements you select are to be excluded from the table or included. If you select "Exclude in Table", the elements you select will not be included in the table. The other elements in "Available items" will be included in the table.

If you wish to exclude a small proportion of the available elements, it would be quicker to select the elements that are to be excluded. However, if you wish to include only a small proportion of the elements, it would be quicker to select "Include in Table". The elements selected will then be displayed in the table, and all the other elements in "Available items" will not be displayed in the table.

Figure 2 - Selecting items to be masked

Numeric Mask

This property provides a simple way of excluding from calculations values from numeric variables. Click the + icon beside the property to open the options fields .

Figure 3 - The Numeric Mask property

The options are:

• Show all - default, no selections made.
• Show specified range - upper and lower limit check boxes become available, and if selected associated fields appear into which you type the required limiting values.
• Show Specified Values - a field appears into which you type the values that you want to show. Type multiple values separated by a comma.
• Hide specified range - upper and lower limit check boxes become available, and if selected associated fields appear into which you type the required limiting values.
• Hide Specified Values - a field appears into which you type the values that you want to hide. Type multiple values separated by a comma.

Filter by Mask

When you apply a mask to a question, for example to exclude the "I have no favorite" row, you may also want to exclude these responses from the base calculations so that the percentages of the remaining items add up to 100%. Check the Filter by mask box to exclude the masked responses when calculating percentages . This functionality is particularly useful when you have several questions stacked in the same table.

Figure 4 - The "complete" table

Figure 5 - The same table with "I have no favorite" masked but without "Filter by Mask" - the percentages don't add up

Figure 6 - The same table with "I have no favorite" masked and with "Filter by Mask" set

The illustrations show the same table with the results of a "what is your favorite" question against the respondent's age. The top table shows the "complete" table, including the "I have no favorite" results, where the total base is 146 and the percentages in the columns add up to 100%. The second table has the "I have no favorite" results masked so the row is removed from view. However as the table is not filtered by the mask the results are still included in the calculations, so the total base is still 146 and the percentages in the columns no longer add up to 100%. The final table also has the Filter by Mask property set. Here the "I have no favorite" results are removed from the calculations, reducing the total base to 108 and changing the remaining percentage values accordingly so that the columns now total 100%.

You can use the Filter by Mask property to exclude certain categories, numeric codes or ranges from statistical computations. The Filter by mask option and the appropriate mask settings (answer mask/scale mask/numeric mask depending on the variable type) is available both in collapsed and uncollapsed state. If filtering by mask is turned on then the appropriate filter will be applied regardless of the collapsed state of the question. This can be used to include/exclude certain codes or ranges (i.e. 99) when computing averages or other statistics.

Numeric mask settings include the "exclude range" and "exclude codes" options so that both inclusive and exclusive filtering can be specified.