Create a new survey
or open a saved survey from the **My Surveys** page. The
**Design** tab opens. Click the **Analyze** tab. The
**My Reports** page opens. Select the **Cross-tab Analysis**
report from the **Other Reports** section. The report editing
dialog opens. Click the **Properties** tab.

Use the significance testing to compare whether the proportion of respondents in one column is significantly different from the proportion in the other column within the single variable. You can use different confidence intervals for the significance testing.

In the 6.1 release, you can perform
the significance testing on the “Choose One” (including the “Matrix” sides)
variables using the **Cross-tab Analysis** report. You can
use the significance testing to compare whether the proportion of respondents
in one column is significantly different from the proportion in the other
column within the single variable. To manage the significance
testing options, access the **Properties** tab in your **Cross-tab
Analysis** report. See image below.

**Significance Testing**– Use this drop-down list to turn on or turn off the significance testing on the “Choose One” variables by selecting the “On” or “Off” option correspondingly. “Off” is a default option.**Confidence Interval**– Select the confidence interval for significance testing from the drop-down list. The available options are 90%, 95%, and 99%. “95%” is a default option.

**Note: For
the steps on how to create the Cross-tab Analysis report, see the “Cross-tab
Analysis Report” topic.**

When you perform the significance testing, the reference letters show as the column ID in the column headers below the column titles. For the columns 1-26, lowercase English letters are shown (a, b, c, …, y, z), and, for the columns 27-52, uppercase English letters are shown (A, B, C, …, Y, Z). If the difference between the columns is significant, the ID of one column shows under the response data of the other column. See image and example below.

As the report contains four columns in this example, the letters “a,” “b,” “c,” and “d” show up in the column headers. The result of significance testing is that the respondents who have selected the “Chicago” choice are significantly different from those who have selected the “New York” choice. Thus, the “b” letter shows in the cell in the “Chicago” row and “a” column, and the “a” letter shows in the cell in the “New York” row and “b” column.

If the number of degrees of freedom (responses) is less than 30, no significance testing is calculated and published, and a footnote on the table states “Base too small for significance testing between columns [a-b, a-c, b-c].” If the number of degrees of freedom is less than 100, the significance testing is calculated and published, and a footnote on the table states “Caution – small bases for columns [c-d, c-e, c-f].” Depending on the selected confidence interval, a footnote showing the chosen risk level appears on the table. For example, if you select the 95% confidence interval, a footnote states “Proportions: Columns Tested (5% risk) [a-c, b-c, a-c].”

The significance testing is not saved if you close the report. When you open the saved report later, the previous test results are cleared. You can perform a new test if you want.

You can also export the significance testing results to the Microsoft
Excel file format as a part of the **Cross-tab Analysis** report to
view the test data outside the Vovici product.

Vovici uses the same significance test calculations as described in Quantum’s Special T statistics (Quantum volume 3, Section 7) for the T-test on column proportions. This example compares the values of the proportions in two columns of a table. For each of the two columns (k=1, 2), the sample proportions are defined as:

P1 = Cell frequency 1 / Base 1

P2 = Cell frequency 2 / Base 2

Population variance is calculated as:

P = (Cell frequency 1 + Cell frequency 2) / (Base 1 + Base 2)

The variable T is calculated as:

T = (P1 – P2) / Sqrt (p x (1-p) x (1 / Base 1 + 1 / Base 2) / (1 – 1 / (Base 1 + Base 2)))

1. Create a **Cross-tab Analysis** report
from the **My Reports** page. The **Name Your Report**
dialog opens. See image below.

2. Type the name of a report in the “Report Name” field.

3. Click **OK**. The dialog
opens where you can define your **Cross-tab Analysis** report properties.

4. On the **Properties** tab, select the
“On” option from the “Significance Testing” drop-down list.

5. Select the confidence interval for significance testing from the “Confidence Interval” drop-down list.

6. Click **OK**. The report
is generated with the significance testing.

1. Navigate to the **Administration** tab.

2. In the left pane, click the **General
Setup** subtab.

3. Select the “Disable Significance Testing in Cross-tab Analysis” check box. See image below.

4. Click **Save Setup**.

See Also