document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=914107>Question 914107</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The duration of phone calls to a Calling Centre is normally distributed with a mean of <BR>\n" );
document.write( "seven minutes and a standard deviation of two minutes. Calculate the probability that a <BR>\n" );
document.write( "phone call to the Calling Centre last for between 5 to 10 minutes.<BR>\n" );
document.write( "(b) A recent survey found that 56% of mobile phone users, between the ages of 18 to 34, <BR>\n" );
document.write( "had a smartphone. Suppose a random sample of 100 mobile phone users were selected. <BR>\n" );
document.write( "What is the probability that less than 50 of them have a smartphone? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #554870 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=554870\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\">  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=z+=blue+%28x+-+mu%29%2Fblue%28sigma%29 ALIGN=MIDDLE  ALT=\"z+=blue+%28x+-+mu%29%2Fblue%28sigma%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > mean = 7, sd = 2<BR>\n" );
document.write( "P( 5 < x < 10) = normalcdf(-100, 3/2) - normalcdf(-100, -1) = .9332 - .1587 = .7745 0r 77.45%<BR>\n" );
document.write( "0r may Use <BR>\n" );
document.write( "P( 5 < x < 10) = normalcdf(-1, 3/2)<BR>\n" );
document.write( "P( 5 < x < 10) Area between the green lines (z = -1   and z = 1.5)<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=drawing%28400%2C200%2C-5%2C5%2C-.5%2C1.5%2C+graph%28400%2C200%2C-5%2C5%2C-.5%2C1.5%2C+exp%28-x%5E2%2F2%29%29%2C+green%28line%281.5%2C0%2C1.5%2Cexp%28-1.5%5E2%2F2%29%29%2Cline%28-1%2C0%2C-1%2Cexp%28-1.00%5E2%2F2%29%29%29%2Clocate%284.8%2C-.01%2Cz%29%2Clocate%284.8%2C.2%2Cz%29%29 ALIGN=MIDDLE   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "..........<BR>\n" );
document.write( " <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=z+=blue+%28x+-+mu%29%2Fblue%28.56%2A.44%2Fsqrt%28100%29%29%29 ALIGN=MIDDLE  ALT=\"z+=blue+%28x+-+mu%29%2Fblue%28.56%2A.44%2Fsqrt%28100%29%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "b) P( x < .50) = normacdf(-100, -1.2087) = .1134 0r 11.34%<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=z+=blue+%28.50+-+.56%29%2Fsqrt%28.56%2A.44%2F%28100%29%29 ALIGN=MIDDLE  ALT=\"z+=blue+%28.50+-+.56%29%2Fsqrt%28.56%2A.44%2F%28100%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = -1.2087 </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );