A new design for the braking system on a certain type of car has been proposed. For the current system, the true average braking distance at 40 mph under specified conditions is known to be 120 ft. It is proposed that the new design be implemented only if sample data strongly indicates a reduction in true average braking distance for the new design.
(a) Define the parameter of interest.
μ = true average braking distance for the old design
p̂ = true proportion of cars whose braking distances did not reduce
p̂ = true proportion of cars whose braking distances reduced
μ = true average braking distance for the new design
State the relevant hypotheses.
H0: μ = 120
Ha: μ > 120
H0: p̂ = 120
Ha: p̂ <
120
H0: μ = 120
Ha: μ ≠ 120
H0: μ = 120
Ha: μ < 120
H0: p̂ = 120
Ha: p̂ ≠ 120
(b) Suppose braking distance for the new system is normally
distributed with σ = 11. Let X denote the sample
average braking distance for a random sample of 36 observations.
Which values of x are more contradictory to
H0 than 117.2?
x ≤ 117.2
x ≥ 117.2
What is the P-value in this case? (Round your answer to
four decimal places.)
What conclusion is appropriate if α = 0.10?
The new design does have a mean breaking distance less than 120 feet at 40 mph.
The new design does not have a mean breaking distance less than 120 feet at 40 mph.
(c) What is the probability that the new design is not implemented
when its true average braking distance is actually 115 ft and the
test from part (b) is used? (Round your answer to four decimal
places.)
Please show me how to work part (c). The answer is not .8849. It is supposed to be .0741 but I do not know how to get it.
Note: In part (c), it was asked the type II error probability.
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