A marginal table organizes survey counts by variables while placing aggregate totals along the row and column margins. Those totals answer probability questions before or after additional evidence is observed. section 13.1
Cold and sneezing survey
In a survey of 10,000 people, the margins show that 1,000 have colds, establishing a 10% prior probability. Among the 1,000 people with colds, 860 sneezed, giving P(S|C) = 86%. section 13.1
Table 13.1 A survey of 10,000 respondents organized in a marginal table
| Cold: YES |
Cold: NO |
Total |
|
|---|---|---|---|
| Sneezed: YES |
860 |
270 |
1,130 |
| Sneezed: NO |
140 |
8,730 |
8,870 |
| Total |
1,000 |
9,000 |
10,000 |
Use the table to trace how row and column totals support prevalence estimates and conditional-probability calculations. section 13.1
