StatWise Sample Size Calculator
Calculate sample size for comparing continuous outcomes
Means
Calculate sample size for comparing proportions
Proportions
Input Parameters
The probability of incorrectly concluding an effect exists when it doesn't (typically 0.05)
Significance Level (alpha)
The probability of correctly detecting an effect when it exists (typically 0.8)
Power (1 - beta)
Average outcome value of all subjects in Group 1 (e.g., 150)
Mean of Group 1
Average outcome value of all subjects in Group 2 (e.g., 125)
Mean of Group 2
How much individual subject outcomes differ from the group average (e.g., 20)
Standard Deviation (common)
Ratio for number of subjects in Group 1 to Group 2 (e.g., if 1:1 ratio, enter 1; if 1:2 ratio, enter 0.5; if 2:1 ratio, enter 2)
Allocation Ratio (n1/n2)
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Input Parameters
The probability of incorrectly concluding an effect exists when it doesn't (typically 0.05)
Significance Level (alpha)
The probability of correctly detecting an effect when it exists (typically 0.8)
Power (1 - beta)
The anticipated percentage of subjects in Group 1 who will have the response/or event (e.g., if 30%, enter 0.3)
Proportion in Group 1
The anticipated percentage of subjects in Group 2 who will have the response/or event (e.g., if 25%, enter 0.25)
Proportion in Group 2
Ratio for number of subjects in Group 1 to Group 2 (e.g., if 1:1 ratio, enter 1; if 1:2 ratio, enter 0.5; if 2:1 ratio, enter 2)
Allocation Ratio (n1/n2)
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