document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1032526>Question 1032526</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Suppose we wish to obtain 95% confidence interval for proportion of teachers who believe algebra should be required for every student graduating high school.  We wish to have a margin of error 4%. How many subjects must we sample if: a. We don't know anything about the previous proportion. b. We took a sample previously and found that 23% of teachers believe Algebra should be required.  c. What is the difference between parts a and b?  How and why are they different? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #647186 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=647186\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Suppose we wish to obtain 95% confidence interval for proportion of teachers who believe algebra should be required for every student graduating high school. We wish to have a margin of error 4%. How many subjects must we sample if:<BR>\n" );
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document.write( "a. We don't know anything about the previous proportion.<BR>\n" );
document.write( "n = [1.96/0.04]^2*(1/2)^2 = 600<BR>\n" );
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document.write( "b. We took a sample previously and found that 23% of teachers believe Algebra should be required.<BR>\n" );
document.write( "n = [1.96/0.04]^2*0.23*0.77 = 425<BR>\n" );
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document.write( "c. What is the difference between parts a and b?<BR>\n" );
document.write( "Taking a sample gave you more information.<BR>\n" );
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document.write( "How and why are they different?<BR>\n" );
document.write( "See above.<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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