SOLUTION: 4) The strength limit of a specific type of a cable is random variable with mean value of 1500 kg and standard deviation 175 kg. The factory that manufactures this type of cables c

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Question 1183649: 4) The strength limit of a specific type of a cable is random variable with mean value of 1500 kg and standard deviation 175 kg. The factory that manufactures this type of cables claims that they improved the materials that they used and the new resistance limit of the cable has increased. We randomly chose a sample of 50 cables and the mean strength limit was 1570 kg. If the strength limit in the specific type of cable is normally distributed with a significance level of 0.05, can we state that the claim of the manufacture factory is true? Justify your answer.
Answer by Boreal(15235) (Show Source):
You can put this solution on YOUR website!
Ho: strength <=1500
Ha: strength >1500
alpha=0.05 p{reject Ho|Ho true}
test stat is z
reject Ho for z>1.645
calculation is z=(x-mean)/sigma/sqrt(n)
=70/(175/sqrt(50))
=2.83
reject Ho and conclude the claim is correct, the strength is greater.