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 may lack power to detect real effects. The document also discusses how power and effect size determine the likelihood of correctly rejecting the null hypothesis and avoiding Type II errors.