Answer:
Then z(s) is out of the acceptance region, we reject H₀, doubts of the independent testing firm are valids
Step-by-step explanation:
We will develop a Hypothesis Test ( a 2 tail test since the independent testing firm is interested in finding out if there is an incorrect MPG rating from the manufacturer
Test Hypothesis :
Null hypothesis H₀ μ = μ₀
Alternative Hypothesis Hₐ μ ≠ μ₀
Significance Level α = 0,05 α/2 = 0,025
z(c) for α/2 from z-table z(c) = - 1, 96 and by symmetry z(c) = 1,96
Calculating z(s)
z(s) = ( μ - μ₀ ) / σ /√n
z(s) = ( 37,8 - 37,4 ) / 2,3 /√280
z(s) = 0,4 * 16,73 / 2,3
z(s) = 2,90
Comparison between z(c) and z(s)
z(s) > z(c) 2,90 > 1,96
Then z(s) is out of the acceptance region, we reject H₀, doubts of the independent testing firm are valids
