The rejection region in hypothesis testing is the range of values for which the null hypothesis is not probable, leading to its rejection. It is determined by the significance level and the critical value, and it helps in deciding whether to accept or reject the null hypothesis based on sample data.
Statistical testing is a method used to make inferences about a population based on sample data, determining the likelihood that observed differences or relationships are due to chance. It involves setting up a null hypothesis, which is tested against an alternative hypothesis, using a significance level to decide whether to reject the null hypothesis.