The document discusses null hypothesis significance testing (NHST) and power. It explains that NHST is used to determine if mean differences between groups are greater than would be expected by chance. A statistically significant result is one that has a low probability of occurring if the null hypothesis is true. The level of significance is typically set at p<.05. Limitations of NHST include that small sample sizes can lead to a lack of power to detect effects. Power refers to the likelihood of correctly rejecting the null hypothesis and depends on sample size, significance level, and effect size. Prospective power analyses estimate the needed sample size while retrospective analyses determine a study's power based on its parameters.