document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=924488>Question 924488</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The average monthly cellular bill is $73. Suppose local monthly household call phone bills are normally distributed with a standard deviation of $11.35.\r<BR>\n" );
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document.write( "a. What is the probability that a randomly selected monthly cell bill is less than $100<BR>\n" );
document.write( "b. what is the probability that a randomly selected monthly cell bill is between $70 and $90. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #560886 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=560886\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> mean = 73, sd = 11.35, <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=z+=+blue%28x+-+73%29%2Fblue%2811.35%29 ALIGN=MIDDLE  ALT=\"z+=+blue%28x+-+73%29%2Fblue%2811.35%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >    <BR>\n" );
document.write( "Using the z-value to determine the Probability:<BR>\n" );
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document.write( "And...Using a TI calculator 0r similarly a Casio fx-115 ES plus<BR>\n" );
document.write( "P( x < 100) = P( z < 27/11.35) = P( z < 2.3788) = normalcdf(-100, 2.3788) = .9913<BR>\n" );
document.write( "......<BR>\n" );
document.write( "For the normal distribution: Below:  z = 0, z = ± 1, z= ±2 , z= ±3 are plotted.  <BR>\n" );
document.write( "<u>Area under the standard normal curve to the left of the particular z</u> is P(z < than its value)<BR>\n" );
document.write( "Note: z = 0 (x value: the mean) 50% of the area under the curve is to the left and 50%  to the right<BR>\n" );
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