In those scenarios, whether it be a change to website design or marketing messaging, you control for as much as possible, determine the success metrics and required sample sizes, change that one thing and let the experiment run.
For prevalence estimates, the required sample sizes depend on the expected prevalence, the desired precision of the estimate and the chosen confidence level (e.g. 90, 95, or 99%).
It was found that the required sample sizes and observable effect sizes varied considerably between different TWI maps and for different ROIs.
Using the centrum semiovale as a reference region reduced the required sample sizes: 3 (putamen and thalamus) to 9 (caudate head).
Numerical results indicate that the required sample sizes could be smaller than that recommended by the FDA for a single trial, especially when the pilot study provides strong evidence in favor of bioequivalence.
This study examines what happens to the type I error, power, and required sample sizes when one efficacy outcome and one correlated safety outcome are monitored simultaneously using sequential designs.
To help readers employ the results presented here, tables are provided to summarize the resulting minimum required sample sizes for cluster randomization trials with two arms and three arms in a variety of situations.
In this Investigators' Corner I discuss why such planning is necessary, give an intuitive introduction to the calculations needed to determine required sample sizes, and hint at some of the more technical difficulties inherent in this aspect of study planning.
A method is presented for reducing the required sample sizes for reporting energy savings with predetermined statistical accuracy in lighting retrofit measurement and verification projects, where the population of retrofitted luminaires is to be tracked over time.
To determine required sample sizes, we estimated (Thalheimer & Cook, 2002) the effect size reported in Wolfe et al.'s (2007) Experiment 7 one of the only studies with a manipulation that reduced miss errors in a low-prevalence search task.
Finally we calculated the required sample sizes in the surveys for a trend to be statistically significant.
