We examine the most common type of hypothesis testing, null hypothesis testing, through three examples: the Z test, Pearson's chi-squared test, and [several forms of] the T-test. By seeing how different questions can be answered using the same formalism, we think through the meaning of terms like null hypothesis, null distribution, test statistic, and significance level. We address p-values only briefly and do not touch on confidence intervals; those will be covered in later chapters.