A manufacturer of hard safety hats for construction workers is concerned about t
ID: 2949489 • Letter: A
Question
A manufacturer of hard safety hats for construction workers is concerned about the mean and the variation of the forces helmets transmit to wearers when subjected to a standard external force. The manufacturer desires the mean force transmitted by helmets to be 800 pounds (or less), well under the legal 1,000-pound limit, and ? to be less than 40. A random sample of n = 45 helmets was tested, and the sample mean and variance were found to be equal to 850 pounds and 2,380 pounds2, respectively.
(a) If ? = 800 and ? = 40, is it likely that any helmet, subjected to the standard external force, will transmit a force to a wearer in excess of 1,000 pounds? Explain. (Use ? = 0.05.)
This answer has not been graded yet.
(b) Do the data provide sufficient evidence to indicate that when the helmets are subjected to the standard external force, the mean force transmitted by the helmets exceeds 800 pounds? (Use ? = 0.05.)
State the null and alternative hypotheses.
H0: ? > 800 versus Ha: ? = 800H0: ? = 800 versus Ha: ? < 800 H0: ? = 800 versus Ha: ? > 800H0: ? > 800 versus Ha: ? < 800H0: ? = 800 versus Ha: ? ? 800
State the test statistic. (Round your answer to three decimal places.)
t =
State the rejection region. (If the test is one-tailed, enter NONE for the unused region. Round your answers to three decimal places.)
State the conclusion.
H0 is not rejected. There is sufficient evidence to indicate that the mean force transmitted by the helmets exceeds 800 pounds.H0 is rejected. There is sufficient evidence to indicate that the mean force transmitted by the helmets exceeds 800 pounds. H0 is not rejected. There is insufficient evidence to indicate that the mean force transmitted by the helmets exceeds 800 pounds.H0 is rejected. There is insufficient evidence to indicate that the mean force transmitted by the helmets exceeds 800 pounds
t > t <Explanation / Answer
Solution B:
given the mean force transmitted by the helmets exceeds 800 pounds
H0:m=800
H1:mu>800
alpha=0.05
? = 800 versus Ha: ? > 800
State the test statistic.
t=sample mean-[population mean/samplesd/sqrt(sample size)
sample sd=sqrt(variance)=sqrt(2380 )=48.78524
t=850-800/48.78524/sqrt(45)
t=6.875
State the test statistic. (Round your answer to three decimal places.)
t=6.875
State the rejection region. (If the test is one-tailed, enter NONE for the unused region. Round your answers to three decimal places.)
its one tail test
right tail.
use excel
=T.INV(0.05;44)
-1.680229977
T>1.680
CONCLUSIN:
T>T CRIT
6.875>1.680
REJECT HO
H0 is rejected. There is sufficient evidence to indicate that the mean force transmitted by the helmets exceeds 800 pounds.
-1.680229977
T>1.680
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