Hello. I could like to calculate the risk difference between two groups for an outcome, using the
Code:
cs
command.
But I am confused by the output which shows P value is >0.05 whereas the 95% CI doesn't cover 0.

Perhaps it is related to the low incidence of the outcome. But how are the P value and 95% CI calculated and why don't they match?

Thank you very much!

Below are the output

. cs case exp [fw=pop]

| exp |
| Exposed Unexposed | Total
-----------------+------------------------+------------
Cases | 2 59 | 61
Noncases | 1342 11717 | 13059
-----------------+------------------------+------------
Total | 1344 11776 | 13120
| |
Risk | .0014881 .0050102 | .0046494
| |
| Point estimate | [95% Conf. Interval]
|------------------------+------------------------
Risk difference | -.0035221 | -.0059456 -.0010986
Risk ratio | .2970137 | .0726542 1.214206
Prev. frac. ex. | .7029863 | -.2142064 .9273458
Prev. frac. pop | .0720132 |
+-------------------------------------------------
chi2(1) = 3.23 Pr>chi2 = 0.0721


. cs case exp [fw=pop], exact

| exp |
| Exposed Unexposed | Total
-----------------+------------------------+------------
Cases | 2 59 | 61
Noncases | 1342 11717 | 13059
-----------------+------------------------+------------
Total | 1344 11776 | 13120
| |
Risk | .0014881 .0050102 | .0046494
| |
| Point estimate | [95% Conf. Interval]
|------------------------+------------------------
Risk difference | -.0035221 | -.0059456 -.0010986
Risk ratio | .2970137 | .0726542 1.214206
Prev. frac. ex. | .7029863 | -.2142064 .9273458
Prev. frac. pop | .0720132 |
+-------------------------------------------------
1-sided Fisher's exact P = 0.0432
2-sided Fisher's exact P = 0.0871