How do I read a crosstab

A typical crosstab might be laid out as follows. There will be some variance depending on the software package used. This example, based on a Choices crosstab, shows internet usage for the total population and the AB social grade in ROI.

Elements………………..Total (Adults)………………………Social Grade (AB)

Sample……………………… 2,047………………………………….. 348
(000)…………………………  2,443…………………………………   403
Vert%………………………..   69.3………………………………….. 84.9
Horz%……………………….  100…………………………………… 16.5
Index…………………………. 100……………………………………  122

Sample: The number of respondents. In total 2,047 respondents use the internet. 348 AB respondents do so.

(000): Respondent figures upweighted as a proportion of the national population. 2,443,000 Irish adults use the internet. 403,000 ABs do so.

Vert%: 69% of adults and 85% of ABs use the internet.

Horz%: 100% of internet users are (in this case) Irish adults. 17% of internet users are ABs.

Index: Propensity relative to the average (average = 100). AB adults are 22% more likely than the average to use the internet. As index values refer to the correlation between variables, it is also valid to say that internet users are 22% more likely to be AB. To ensure sufficient margin for error, only values above 120 or below 80 should be taken as evidence of a positive or negative correlation. Values in the range 80-120 should be considered average.