document.write( "Question 1152814: Assume that when adults with smartphones are randomly​ selected, 57​% use them in meetings or classes. If 7 adult smartphone users are randomly​ selected, find the probability that at least 2 of them use their smartphones in meetings or classes. \n" ); document.write( "
Algebra.Com's Answer #774928 by ikleyn(52908)\"\" \"About 
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document.write( "This is a binomial distribution type problem, where the probability under the question is the sum\r\n" );
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document.write( "     P = \"sum+%28C%287%2Ck%29%2Ap%5Ek%2Aq%5E%287-k%29%2Ck=2%2C7%29\"      (1)\r\n" );
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document.write( "The number of trials is              7;\r\n" );
document.write( "The indexes of success trials        k = 2,3,4,5,6,7\r\n" );
document.write( "The probability of success trial     p = 0.57;\r\n" );
document.write( "                                     q = 1 - p\r\n" );
document.write( "C(n,k) = n! / (k! * (n-k)!)          are binomial coefficients.\r\n" );
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document.write( "I am going to use the Excel standard function BINOM.DIST.\r\n" );
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document.write( "It provides calculations similar sums, but only in the case, when such sums are presented in so called cumulative form\r\n" );
document.write( "as the sums from 0 to some integer number.\r\n" );
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document.write( "Therefore, I convert the sum (1) into the cumulative form.\r\n" );
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document.write( "In cumulative form, the sum  (1)  is equal to  1 - \"sum%28C%287%2Ck%29%2Ap%5Ek%2Aq%5E%287-k%29%2Ck=0%2C1%29\".     (2)\r\n" );
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document.write( "Now, when the sum is presented in cumulative form, you may use the Excel function \r\n" );
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document.write( "BINOM.DIST(1, 7, 0.57, TRUE)  to calculate \r\n" );
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document.write( "    \"sum%28C%287%2Ck%29%2A0.57%5Ek%2A%281-0.57%29%5E%287-k%29%2Ck=0%2C1%29\" = 0.02794.    \r\n" );
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document.write( "In this way, the value of  (2)  is equal to  1 - 0.02794 = 0.97206 (approximately).    ANSWER\r\n" );
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\n" ); document.write( "\n" ); document.write( "On Excel function BINOM.DIST, see its description everywhere, for example\r
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\n" ); document.write( "\n" ); document.write( "To see other probability problems, solved by similar method, look into the lessons\r
\n" ); document.write( "\n" ); document.write( "    - Solving problems on Binomial distribution \r
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