document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=615011>Question 615011</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Amedical researcher wishes to determine  the percentage of females who take vitamins he wishes to be 99% confident that the estimate is within 2 percentage points of the true proportion a recent study of 180 females showed that 25% took vitamins. how large should the sample size be? if no estimate of the sample proportion is available how large should the sample be?\r<BR>\n" );
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document.write( "I do not know how to find what the sample size should be? so I am completely lost on this problem-I don't know where to start help! </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #386972 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=386972\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A medical researcher wishes to determine the percentage of females who take vitamins he wishes to be 99% confident that the estimate is within 2 percentage points of the true proportion a recent study of 180 females showed that 25% took vitamins. how large should the sample size be? if no estimate of the sample proportion is available how large should the sample be? <BR>\n" );
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document.write( "Since E = z*sqrt(pq/n),<BR>\n" );
document.write( "n = [z/E]^2*pq<BR>\n" );
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document.write( "Your 1st problem:<BR>\n" );
document.write( "n = [2.5758/0.02]^2*0.25*0.75 = 3110<BR>\n" );
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document.write( "Your 2nd problem:<BR>\n" );
document.write( "Use p = 1/2 as the best unbiased extimate.<BR>\n" );
document.write( "n = [2.5758/0.02]^2 *0.5*0.5 = 4147 when rounded up<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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