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Table 3 Sample sizes to detect a significant difference in overall mortality. Numeric Results with Proportion Lost to Follow Up = 0.0200

From: The TEAM trial: Safety and efficacy of endovascular treatment of unruptured intracranial aneurysms in the prevention of aneurysmal hemorrhages: A randomized comparison with indefinite deferral of treatment in 2002 patients followed for 10 years

      

Hazard Two-sided

 

Power

N

N1

N2

S1

S2

Ratio

Alpha

Beta

0.8002

1520

760

760

0.8200

0.8800

0.6442

0.0167

0.1998

0.8004

1089

545

544

0.8200

0.8900

0.5872

0.0167

0.1996

0.8003

2125

1063

1062

0.8300

0.8800

0.6861

0.0167

0.1997

0.8005

1437

719

718

0.8300

0.8900

0.6254

0.0167

0.1995

0.8001

3219

1610

1609

0.8400

0.8800

0.7332

0.0167

0.1999

0.8000

2002

1001

1001

0.8400

0.8900

0.6684

0.0167

0.2000

0.8001

5543

2772

2771

0.8500

0.8800

0.7866

0.0167

0.1999

0.8001

3025

1513

1512

0.8500

0.8900

0.7170

0.0167

0.1999

0.8000

12068

6034

6034

0.8600

0.8800

0.8476

0.0167

0.2000

0.8001

5194

2597

2597

0.8600

0.8900

0.7727

0.0167

0.1999

0.8000

46657

23329

23328

0.8700

0.8800

0.9179

0.0167

0.2000

0.8000

11271

5636

5635

0.8700

0.8900

0.8368

0.0167

0.2000

  1. Summary Statements: A two-sided log rank test with an overall sample size of 2002 subjects (of which 1001 are in group 1 and 1001 are in group 2) achieves 80% power at a 0.0167 significance level to detect a difference of 0.0500 between 0.8400 and 0.8900 – the proportions surviving in groups 1 and 2, respectively. This corresponds to a hazard ratio of 0.6684. The proportion of patients lost during follow up was 0.0200.
  2. Software: PASS 2000, Power Analysis and Sample Size for Windows; NCSS, Kaysville, Utah