Question 460429
{{{sigma(x1-x2)=sqrt((s1^2/n1^2)+(s2^2/n2^2))}}}
={{{sqrt((4.3^2/32^2)+(4^2/32^2))}}}
=.1835
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{{{z=(x1-x2)/sigma(x1-x2)=((4.3-4.0)/.1835)=1.63}}}
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For a confidence level of 0.10 the region of rejection begins at 1.64 so  the mechanic cannot support the claim that the mean pipe lengths are different for the two types of pipes.
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Ed