1. Determine the significance level (α): This represents the probability of rejecting the null hypothesis when it's actually true (often denoted by alpha). Common choices are 0.05 (5%) and 0.01 (1%).
2. Identify the type of test: This could be one-tailed (looking for an extreme value in one direction) or two-tailed (looking for extreme values in both directions).
3. Find the relevant degrees of freedom: This value depends on your specific test and sample size. Consult your textbook or online resources for guidance on calculating degrees of freedom for your specific test.
4. Look up the critical value based on α, degrees of freedom, and test type:
Z-test: Use a standard normal distribution table (also called a z-table) to find the critical value. If it's a two-tailed test, you'll need to find two critical values, one for each tail, by dividing α by 2 and looking up the values corresponding to those two significance levels.
T-test: Use a t-distribution table, specifying the degrees of freedom and α level. Similar to the z-test, for a two-tailed test, divide α by 2 and look up the values for each significance level.
Chi-square test: Use a chi-square distribution table, specifying the degrees of freedom and α level.