How to Compare Significant Differences Between Columns

This article describes how to go from a default table with columns that represent different categories:

To a table which also shows the significant differences between the columns within each row:

Requirements

• Familiarity with Displayr's significance testing settings. See How to Apply Significance Testing in Displayr
• A document containing a table that is cross-tabbed by a variable so that each column represents a different category. 

Method

To perform column comparisons in Displayr:

• In the Object Inspector , select Appearance > Appearance > Significance > Compare Columns
  
   
• You can also Specify Columns to be Compared in a Table if needed. You must select a column header before going to the Appearance > Appearance > Significance > Advanced menu. This is because the columns tested are set for a variable set for all tables, and not for individual tables. More specifics are in this article.

The letters are interpreted as follows:

• The letters at the base of the table indicate the names of the columns (i.e., in this case: A, B, C, and D).  
• Where letters appear in a cell, this indicates that the percentage in that cell is significantly higher than the percentage in the same row for the column represented by the letter. For example, the letter "C" that appears for Coca-Cola in the Under 30 column indicates that the 53% preference for Coca-Cola among people aged less than 30 is significantly higher than the value of 34% for people aged 40 or more in column C.  Similarly, we can see that the preference for Coca-Cola among the 30 to 39-year-old group is also significantly higher than for people aged 40 or more.
• The absence of column letters is also informative.  Since no letters are shown on the Coke Zero row, this indicates that there are no significant differences in preference for Coke Zero among the different age groups.
• By default, letters that are significant at the 99.9% confidence level (i.e., p <= 0.001) are represented by capital letters. Lower-case letters are used to represent confidence levels between the 95% and 99.9% levels.  In the table above, all the results are significant at between the 95% and 99.9% levels of significance.   

Restore to Document Default Settings

To revert to the document's current default settings:

• Click the Restore button 

Note: The Restore button will only be enabled when settings for the selected item(s) are different from the document's current default settings (settings saved by Set as Default). The Restore button will be disabled if you do not save any settings for the selected item(s). See: How to Set the Default Type of Significance Test to learn more about changing the default settings.

See Detail from Statistical Testing

If you'd like more information on how these settings are used in the testing on your table, you can investigate the specific statistical test, see intermediary calculations, and get a description of what is being tested by using the Statistical Test (alpha) feature, see How to See Statistical Testing Detail Using a Table. When comparing columns, you would select both cells in the row that you'd like to compare to see the underlying test detail before using the alpha button.

Next

How to Apply Significance Testing in Displayr

How to Specify Columns to be Compared in a Table

How to Set the Default Type of Significance Test

How to Conduct Significance Tests by Comparing to Previous Periods

How to Change the Overall Confidence Level and Column Comparisons at Which Significant Differences are Displayed

How to Apply Multiple Comparison Correction to Significance Tests