document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1182925>Question 1182925</A>: <I><SPAN STYLE=\"word-break: break-all;\">  Suppose the age a female has her first period is normally distributed with a mean age of<BR>\n" );
document.write( "12 years and standard deviation of 2.5 years.<BR>\n" );
document.write( "a. Calculate the probability of randomly selecting a female who will have her first<BR>\n" );
document.write( "period after 14 years.<BR>\n" );
document.write( "b. Calculate the probability of randomly selecting a female who will have her first<BR>\n" );
document.write( "period before 10 years old.<BR>\n" );
document.write( "c. Calculate the percentage of females who will have their first period between 12 years<BR>\n" );
document.write( "old and 17 years old.<BR>\n" );
document.write( "d. A man has a daughter who is now 21 years old and still did not have her first period.<BR>\n" );
document.write( "Should he be worried? Explain based on your knowledge of variables that follows a<BR>\n" );
document.write( "normal distribution.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #813143 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=813143\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> z=(x-mean)/sd<BR>\n" );
document.write( ">(14-12)/2.5 is z>0.8 with probability 0.2119<BR>\n" );
document.write( "-<BR>\n" );
document.write( "< (10-12)/2.5 is z < -0.8 with same probability of 0.2119<BR>\n" );
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document.write( "between 12 and 17, this will be with z between 0 and 2 with probability 0.4772<BR>\n" );
document.write( "also 2ndVARS 2 normalcdf(12,17,12,2.5) ENTER<BR>\n" );
document.write( "-<BR>\n" );
document.write( "greater than 21 will be a z>9/2.5 or 3.6 with probability 0.00016. This is very low probability from a statistical standpoint and by age 15 without one a girl has the diagnosis of primary amenorrhea and should be evaluated for hormonal and other issues. </SPAN>\n" );
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