document.write( "Question 1090504: In the study of fingerprints, an important quantitative characteristic is the total ridge count for the 10 fingers of an
\n" ); document.write( "individual. The University Management and Technology uses thousands of fans each year. The brand of fans it currently
\n" ); document.write( "has a mean life of 9000 hours. A manufacturer claims that its new brand of fans, which cost the same as the brand the
\n" ); document.write( "university currently uses, has a mean life of more than 9000 hours. The university has decided to purchase the new brand
\n" ); document.write( "if, when tested, the test evidence supports the manufacturer’s claim at the .05 significance level. Suppose 64 fans were
\n" ); document.write( "tested with sample mean x  9200 hours and standard deviation S = 800 hours. \n" ); document.write( "
Algebra.Com's Answer #704961 by Boreal(15235)\"\" \"About 
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This is a one-tail test; assume random sample from normal distribution and s is an unbiased estimator of sigma.
\n" ); document.write( "Ho: fans last same or less than old ones
\n" ); document.write( "Ha: fans last longer
\n" ); document.write( "alpha=0.05 P{reject Ho|Ho true}
\n" ); document.write( "test statistic is a t df=63, 0.95
\n" ); document.write( "Critical value is t>1.98
\n" ); document.write( "calculation is t=(9200-9000)/800/sqrt (64)
\n" ); document.write( "this is 200/100 or +2
\n" ); document.write( "This falls beyond the range of the critical value, so the null hypothesis is rejected and the manufacturer's claim is supported.
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