“Does the mean processing time differ from 45 days?” σ is unknown and n = 40. The statistic and table are:

Answer

t with s, read at the ∞ row

Options - A. t with s, read at the ∞ row - B. z with σ, read from the z-table - C. t with 39 df, read at row 30 - D. Paired t with 39 df Why - A. Correct — σ unknown makes it t; df = 39 > 30, so the course reads the ∞ row. - B. No σ was given; a sample s makes it t. - C. Row 30 is not the rule; df above 30 read the ∞ row. - D. One sample of 40 invoices — nothing is paired.

H-W7 (the scenario → distribution chart, REFERENCE for shape only); BCc “one recipe”; every module’s worked examples; original scenarios