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Standard CrosstabsA standard cross tabulation has at least one ROW axis (the Y-axis), and it can optionally have a COLUMN (the X-axis). It displays counts of intersections. A crosstab is created from a table called the resolution table, or owner table. The counts and values displayed in a crosstab are dependent on the owner table from which the crosstab is created. Example 1 of a dimensional crosstab - Y-axis onlyThis simple crosstab displays counts of customers grouped by occupation:
Example 2 of a dimensional crosstab - Y and X axesThis crosstab has an additional COLUMN (X-axis). It displays counts of customers grouped by occupation and age band:
Examples of changing the resolution tableThe examples above are very simple crosstab because both the axes and the resolution table come from the same table. The examples below show how the counts can be modified by changing the crosstab's resolution table. The following simple crosstab displays counts of Households, grouped by occupation. Here it can be seen that there are 5,532 Households containing Directors, implying that some of the 6,120 directors in the system share the same household. Note: some disparity could also be accounted for by a lack of referential integrity.
The same principle applies when you change the resolution table on a two dimensional crosstab. The following crosstab has an additional COLUMN (X- axis) of AgeBand. The crosstab now displays counts of households grouped by Occupation AND AgeBand. Here we can see that there are 202 households containing both a person whose AgeBand is 65 Plus AND a director.
Understanding Standard Crosstab resultsIn the second result the numbers represent the numbers of household records that correspond to the combined values of X and Y axis labels. The number of directors over 65 has increased from 178 to 202 households. How can 178 customers live in 202 households? The explanation is quite simple. The second result set does NOT contain the households in which the 178 people live. It represents the 202 households that contain a director AND someone who is over 65. Although there are only 178 people who satisfy both criteria, there are 202 households that satisfy the criteria. The diagrams below illustrate how the crosstab calculates the results. When the axes are taken from the same table as the resolution table, the same record satisfies the criteria. So in the instance here, there are 178 customer records with Occupation Director and AgeBand 65 Plus:
When the axes are taken from a different table to the resolution table, different records can satisfy the criteria. So in this example, there are 202 households containing both a Director and someone over 65:
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