How to Use the tTable to Solve Statistics Problems
The ttable (for the tdistribution) is different from the Ztable (for the Zdistribution); make sure you understand the values in the first and last rows. Finding probabilities for various tdistributions, using the ttable, is a valuable statistics skill. Use the ttable as necessary to solve the following problems.
Sample questions

For a study involving one population and a sample size of 18 (assuming you have a tdistribution), what row of the ttable will you use to find the righttail (“greater than”) probability affiliated with the study results?
Answer: df = 17
The study involving one population and a sample size of 18 has n – 1 = 18 – 1 = 17 degrees of freedom.

For a study involving a paired design with a total of 44 observations, with the results assuming a tdistribution, what row of the table will you use to find the probability affiliated with the study results?
Answer: df = 21
A matchedpairs design with 44 total observations has 22 pairs. The degrees of freedom is one less than the number of pairs: n – 1 = 22 – 1 = 21.

A tvalue of 2.35, from a tdistribution with 14 degrees of freedom, has an uppertail (“greater than”) probability between which two values on the ttable?
Answer: 0.025 and 0.01
Using the ttable, locate the row with 14 degrees of freedom and look for 2.35. However, this exact value doesn’t lie in this row, so look for the values on either side of it: 2.14479 and 2.62449. The uppertail probabilities appear in the column headings; the column heading for 2.14479 is 0.025, and the column heading for 2.62449 is 0.01.
Hence, the uppertail probability for a tvalue of 2.35 must lie between 0.025 and 0.01.
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