document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=509038>Question 509038</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A company is studying the number of daily debit card purchses. If there were 20 purchases and the probability of a debit card purchase is 0.5. <BR>\n" );
document.write( "a. what is the standard deviation of the number of debit card purchases<BR>\n" );
document.write( "b. based on the shape of the distribution approx 99.7% should be between__and __ </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #341264 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=341264\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A company is studying the number of daily debit card purchases. If there were 20 purchases and the probability of a debit card purchase is 0.5. <BR>\n" );
document.write( "a. what is the standard deviation of the number of debit card purchases<BR>\n" );
document.write( "Ans: sqrt(npq) = sqrt(20*1/2*1/2) = sqrt(5)<BR>\n" );
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document.write( "b. based on the shape of the distribution approx 99.7% should be between__and __<BR>\n" );
document.write( "mean = np = 10<BR>\n" );
document.write( "---<BR>\n" );
document.write( "m-3std = 10-3sqrt(5) is approx 3.29 <BR>\n" );
document.write( "---<BR>\n" );
document.write( "m+3std = 10+3sqrt(5) is approx 16.7<BR>\n" );
document.write( "=====================<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( "======================== </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );