document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=314218>Question 314218</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The lifetime of a certain brand of electric light bulb is known to have a standard deviation of 47 hours. Suppose that a random sample of 50 bulbs of this brand has a mean lifetime of 485 hours. Find a 90% confidence interval for the true mean lifetime of all light bulbs of this brand. Then complete the table below.<BR>\n" );
document.write( "Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place.\r<BR>\n" );
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document.write( "What is the lower limit of the 90% confidence interval?<BR>\n" );
document.write( "What is the upper limit of the 90% confidence interval? </SPAN>\n" );
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