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Example
A 7 year trial is planned using a weighted logrank
statistic to place weight late
•Plan:
–1/28,
2/28, 3/28, …, 7/28 weight over the 7 years
•An
interim analysis conducted after 3 years
–1/6,
2/6, 3/6 over the first three years
•(later
years have no data, hence no weights)