Continuous
Dichotomous
Survival
Clustered
Longitudinal
Study Design
Power Triplet
Typically 0.05
Typically 0.80 or 0.90
Effect Size Parameters
Smallest clinically meaningful difference
From prior studies or pilot data
Allocation
k=1 for equal allocation (most efficient)
Study Design
Power Parameters
Proportion Parameters
Proportion in control group
Expected proportion in treatment group
Allocation
Study Design
Power Parameters
Note: This calculator assumes exponential survival (constant hazard) when converting required events to total sample size.
Hazard Parameters
HR < 1 favors treatment
Study Duration
Time to enroll all subjects
Minimum follow-up after last enrollment
For calculating event probabilities
Allocation
Outcome Type
Power Parameters
Effect Parameters (Continuous)
Cluster Parameters
Correlation within clusters (0-1)
Average number of subjects per cluster
Study Design
Power Parameters
Effect Parameters
Difference in slopes or means
Repeated Measures
Total assessments per subject
Between-measurement correlation