Question

An article presents an analysis of the profit of international construction projects. In a sample of 126 projects, the average profit margin (in percent) was 8.27 with a standard deviation of 16.33. A test is made of H₀ : μ ≥ 10 versus H₁ : μ < 10.

- Find the P-value. Round the answer to four decimal places.

This is what i have, but for some reason I'm being told it is wrong.

(8.27 - 10 ) / (16.33 / sqrt 126) = -1.879 - -> -1.88 -- > Z = .0301

- The P-value calculated for testing H₀ : µ ≥ 10 versus H₁ : µ < 10 is not a small probability, hence it is plausible that the mean profit margin is 10% or more. False.

Answer 1

Yes it is wrong, because population standard deviation is unknown therefore you can't use z test this problem we can solve using t test.

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