document.write( "Question 815721: According to a survey, college students make an average of 11 calls per day on their mobile phone. Moreover, 80% of the students surveyed indicated that their parents pay for their mobile phone expenses.\r
\n" ); document.write( "\n" ); document.write( "If 20 students are selected at random, what is the probability that:
\n" ); document.write( "(i) All 20 have their parents pay for their mobile phone expenses?
\n" ); document.write( "(ii) At least 8 have their parents pay for their mobile phone expenses?
\n" ); document.write( "(iii) No more than 5 students pay for their own mobile phone expenses?\r
\n" ); document.write( "\n" ); document.write( "p=0.8 q=0.2\r
\n" ); document.write( "\n" ); document.write( "(ii) P(x≥8)= 1- P(x<8)
\n" ); document.write( " = 1- 1 - P(0) - P(1)....P(8)???
\n" ); document.write( " = 1- 20C0(0.8)^0(O.2)^20.....20C7(O.8)^7(0.2)^13 ???\r
\n" ); document.write( "\n" ); document.write( "Can you help me to solve all this questions?im lost...thank you very much for your coorporation.
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Algebra.Com's Answer #491200 by ewatrrr(24785) $\"\"$ $\"About$

You can put this solution on YOUR website!

 
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document.write( "Hi,
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document.write( "80% of the students surveyed indicated that their parents pay for their mobile phone expenses. 20 students selected at random. 
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document.write( "Binomial Probability Distribution Values: 
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document.write( "Note: The probability of x successes in n trials is: 
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document.write( "P = nCx*  where p and q are the probabilities of success and failure respectively. 
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document.write( "In this case p = .8 & q = .2 and n = 20  nCx = \r
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document.write( "(i) P(x=20) = (.8)^20(.2)^0 = .0115  0r 1.15%
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document.write( "(ii) At least 8 have their parents pay for their mobile phone expenses?
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document.write( "P(x≥8)= 1- P(x≤7)**  TI Calculator:  1 - binomcdf(20,.80,7)= .999998
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document.write( "excel function : 1 - BINOMDIST(7,20,0.8,TRUE)
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document.write( "(iii) No more than 5 students pay for their own mobile phone expenses? 
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document.write( "         TI Calculator:  binomcdf(20,.80,5) = .00000018
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document.write( "excel function : BINOMDIST(5,20,0.8,TRUE)
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document.write( "If You do not have access to a TI Calculator or an Excel Worksheet,
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document.write( "might recommend STATTREK.com as a reference. \n" );
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