document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=909169>Question 909169</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I am having problems figuring out where to even start with the following, even just a  hit would be appreciated.\r<BR>\n" );
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document.write( "According to a survey, College students make an average of 18 calls per day on their cell phone.  Moreover, 85% of the students surveyed indicated that their parents pay their cell phone expenses.\r<BR>\n" );
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document.write( "a)  If you select a student at random, what is the probability that he or she makes more than 10 calls in a day?  Less than 15 calls a day? At least 20 calls a day?\r<BR>\n" );
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document.write( "b)  If you select a random sample of 15 students, what distribution can you use to model the proportion of students who have parents who pay their cell phone expenses?\r<BR>\n" );
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document.write( "c)  Using the distribution selected in (b), what is the probability that all 15 have parents who pay their cell phone expenses?  At least 10?<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #551703 by </B><A HREF=/tutors/aboutme.mpl?userid=ewatrrr><B>ewatrrr(24785)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ewatrrr><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=ewatrrr><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=551703\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> a) Poisson Distribution (<u>average</u> = 10 per day):<BR>\n" );
document.write( "P( x >10) = 1 - poissoncdf(10,10)<BR>\n" );
document.write( "P( x < 15) = poissoncdf(10,14) <BR>\n" );
document.write( "P(x &#8805; 20) = 1 - poisson(10,19)<BR>\n" );
document.write( "b) Binomial Distribution (parents pay 0r don't pay)<BR>\n" );
document.write( "p(pay) = .85,  n = 15<BR>\n" );
document.write( "c)P(x = 15) = binompdf(15, .80, 15) = .85^15<BR>\n" );
document.write( "P(x  &#8805;  10) = 1 - binomcdf(15, .85, 9)<BR>\n" );
document.write( "Using <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=P+%28x%29=+highlight_green%28nCx%29%28p%5Ex%29%28q%29%5E%28n-x%29+ ALIGN=MIDDLE  ALT=\"P+%28x%29=+highlight_green%28nCx%29%28p%5Ex%29%28q%29%5E%28n-x%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 15C15(.85)^15(.15)^0<BR>\n" );
document.write( "p and q are the probabilities of success and failure respectively. <BR>\n" );
document.write( "In this case p= .85, q = .15 , n = 15<BR>\n" );
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