Prob 9.31

# Prob 9.31 - 9.31 Right-tail test Given 0 = \$47.50(the claim...

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9.31. Right-tail test. Given: μ 0 = \$47.50 (the claim) n = 64 xbar = \$51.00 s = \$12.00 Significance level: Use α = 0.05 a. Mean quarterly water bill is at most \$47.50 as claimed (for the nationwide average) or it is higher (as suggested by the sample). So this is a right-tailed test. H 0 : μ 47.50 H a : > 47.50 This is a right-tailed test. b. 333 . 2 = 64 00 . 12 50 . 47 00 . 51 = = 0 - - n s x t μ Degrees of freedom df = n – 1 = 63 Using t table: Search the row df = 63 for a value of 2.333 or close. Reading across the row for df = 63, the t value 2.333 is between 1.998 and 2.387. Reading up the column from 1.998 to the header, the area = 0.025. Reading up from 2.387 to the header, the area = 0.01. As a result, using t table, the area in upper tail is between 0.025 and 0.01. Therefore, the p -value is between 0.025 and 0.01. Exact p -value corresponding to t = 2.333 is p = 0.0114 (by Excel, for one tail; 0.01 < 0.0114 < 0.025). With a

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Prob 9.31 - 9.31 Right-tail test Given 0 = \$47.50(the claim...

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