This text snippet provides various statistical information and tables related to t-values and z-values for different confidence levels and degrees of freedom. It explains that when sample size is less than 30, a t-score should be used instead of a z-score. The tables show critical values for t-intervals and t-distributions at different confidence levels, and provide instructions on how to find the critical t-value for a given confidence level and sample size. The text also explains the concept of one-tail and two-tail probabilities and how they relate to t-values. Finally, it presents an example problem to demonstrate the use of t-values in a statistical test.