In 2005, the death : case ratio for breast cancer in Canada has been estimated to be 0.24 [ 6].
More controls than cases were recruited (3:1 control to case ratio for the total sample) to maximise statistical power given the small number of cases in the geographic catchments that could be accrued over the study period.
The number of recruits required was based on the estimated number of cases and the expected participation rate among controls, in order to obtain a 1 1 control to case ratio for each group of cases (lung or head and neck).
They proposed a fast approximation algorithm with three different absolute and asymptotic worst case ratios for the jobs have identical sizes, identical processing times and both arbitrary sizes and arbitrary processing times.
The authors correctly point out that a key assumption of the discrete-time Cox proportional hazards model is that the hazard ratio [or, in this case, fecundability odds ratio (fOR)] be constant over the follow-up time.
Koulamas and Kyparisis [3] analyzed a three-stage assembly scheduling problem by minimizing the makespan and analyzed the worst-case ratio bound for several heuristics for this problem.
Compared with several 2-approximation algorithms in the literature, this paper presents an approximation algorithm with a worst case ratio 2−2m+1<2 for any m QCs.
Our pandemic detection algorithm uses two metrics obtained from weekly reported ILI cases: the weekly case ratio (WCR) for cases aggregated across the region and NHB, the number of health boards reporting increases in the cases over the previous week.
Overall, 189/236 (81%) of the control group were either specialists or general practitioners compared with only 29/59 (49%) of the cases (odds ratio for difference 4.16, 95% confidence interval 2.8 to 7.6, P<0.001, unmatched χ analysis).
Using identical invitation letters to cases and controls, we aimed at a 1 1 case-control ratio for women and a 1 2 case-control ratio for men, but all invited subjects who agreed to participate were included.
