Power, precision, and sample size

Before you conduct your experiment, determine the sample size needed to detect meaningful effects without wasting resources. Do you intend to compute confidence intervals (CIs) or perform hypothesis tests? For hypothesis testing, use Stata's power commands or interactive Control Panel to compute power and sample size, create customized tables, and automatically graph the relationships between power, sample size, and effect size for your planned study. For CIs, use Stata's ciwidth commands to do the same but compute precision or CI width instead of effect size and probability of CI width instead of power. To plan a clinical trial using a group sequential design, use Stata's gsdesign commands to compute stopping boundaries and sample sizes.

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