Controls were chosen from strata of length 28 days; days either side of the case day were excluded to reduce the correlation between case and control exposure.
Annual rates of first occurrence per 1000 person-years were calculated and compared as standardized morbidity ratios (SMbR), after indirect standardization by year of entry and by age, each in 4 groups, giving 16 strata, by Breslow and Day's method [ 4], with confidence limits as in mortality data.
Seaside towns are built on strata upon strata of happy memories; a sort of emotional geology.
Virtually all recent applications have used the more robust time stratified variant, with strata being months or day-of-week within month [ 1].
Present-day structure of strata around salt domes may not in every instance coincide with the present-day position of the salt.
Fourth, to assess the impact of choice of time strata, we analysed the data using 14 day (rather than calendar month) time strata to define case and control days.
Thus rock strata C1 C5−1 is rock strata without deformation pressure.
From the Late Cretaceous to this day, overall tectonic uplift and strata denudation occurred in these two basins, and the hydrocarbon generation of the source rocks stopped.
To confirm that timing of initiation relative to index visit did not significantly influence baseline clotting factor and protein levels, patients were stratified and these measurements compared between strata; trends in clotting factors relating to index day were also investigated.
The models were adjusted for precipitation (yes/no), day of the week, holidays (71 days in the entire period), days at the beginning or end of a holiday period (105 days in the entire period), and a strata variable uniquely identifying all combinations of year and month.
