-two-tailed-p-value-approximately-and-how-would-you-compute-it-using-tcdf-bounds

Question

You calculated t = 2.50 for a pairwise comparison with df = 18. Using a graphing calculator's TCDF method (or t-distribution), what is the two-tailed p-value approximately and how would you compute it using TCDF bounds?

Accepted Answer

Approximately p = 0.021; using TCDF you compute one-tail TCDF(2.5, +∞, 18) ≈ 0.0105 and double it.

Answer

Approximately p = 0.0012; multiply the TCDF result by the number of comparisons to get the final value before interpreting.

Answer

Approximately p = 0.082 because TCDF behaves like a normal CDF for df \u003e 10 and requires a continuity correction that reduces the tail areas.

Answer

Approximately p = 0.05 because TCDF returns the two-tailed p directly when you input ±2.5 as bounds with df = 18, so you should set bounds to −2.5 and 2.5 and read the output.