T-test Calculator for RCTs
Kaz's WWC effect size calculator
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What Works Clearinghouse Comparison of Group means (or proportions)

If your outcome is a continuous variable, you fill in all cells.
If your outcome is a binary variable, you still need to fill in all cells, including SD values.
SD values will not affect results, but without them the program would not run.
If binary, you need to use proportions (range 0 to 1), not percentages.

Treatment group N: Treatment group mean: Treatment group SD:
Control group N: Control group mean: Control group SD:

Latest WWC standards
WWC procedures handbook (see page. 14)
WWC standards slides (Definition of small sample size correction, slide 14)