Use Tiwari et al., 2006 modification for CIs

If you are calculating age-adjusted rates or trends in a Rate session, and the Show Standard Errors and Confidence Intervals option is selected, this option will also be available.

When this option is selected, SEER*Stat will calculate confidence intervals for rates and ratio ratios (if included), using the method described in:

Tiwari RC, Clegg LX, Zou Z. Efficient interval estimation for age-adjusted cancer rates. Stat Methods Med Res 2006 Dec;15(6):547-69.

When this option is not selected, SEER*Stat instead uses the methods described in:

Fay MP, Feuer EJ. Confidence intervals for directly standardized rates: a method based on the gamma distribution. Stat Med 1997 Apr 15;16(7):791-801.

Fay MP. Approximate confidence intervals for rate ratios from directly standardized rates with sparse data. Communications in Statistics: Theory and Methods 28(9),2141-60.

The modifications of the gamma (rates) and F intervals (rate ratios) in the Tiwari method are more efficient in the sense that they have empirical coverage probabilities less than or equal to their counterparts and also retain the nominal level.