What is the minimum standard number of subjects typically used in each group of a scientific experiment?

In scientific experiments, using a minimum of 30 subjects in each group is a widely accepted standard because it allows for more reliable statistical analysis. When a larger sample size is utilized, it helps to ensure that the results are more representative of the broader population, thereby reducing the impact of anomalies or outliers that could skew the data. The principle of the central limit theorem underlies this practice; it states that as sample size increases, the sampling distribution of the mean will approach a normal distribution, regardless of the original distribution of the data.

Using 30 subjects is often considered the threshold for achieving sufficient power in statistical tests, enabling researchers to detect true effects or differences if they exist. Sample sizes below this may result in inadequate power, increasing the likelihood of Type I or Type II errors. Therefore, the choice to select 30 subjects serves to enhance the credibility and validity of the experimental outcomes, providing a data foundation that can be confidently analyzed and interpreted. This makes 30 a commonly endorsed standard in the field of scientific research.