document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1135449>Question 1135449</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The number of adults sleep per night is normally distributed with a mean of 6.8 hours. assume that the standard deviation is unknown.\r<BR>\n" );
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document.write( "If 65% of adults sleep more than 6.2 hr/night. what is the variance? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #753601 by </B><A HREF=/tutors/aboutme.mpl?userid=Boreal><B>Boreal(15235)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Boreal><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=Boreal><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=753601\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> z>-0.385 for 65% being more than that value<BR>\n" );
document.write( "z=(x-mean)/sd<BR>\n" );
document.write( "-0.385=(6.2-6.8)/sd<BR>\n" );
document.write( "-0.385 s=-0.6<BR>\n" );
document.write( "s=+1.56<BR>\n" );
document.write( "variance is s^2=2.43 hr^2 (rounding at end)<BR>\n" );
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