document.write( "Question 727550: I am a 12th grade statistics student I am having a hard time understanding my teacher. I was given a work sheet with the following question. a formula but no real instructions. The question is Assume that phone operators give out the correct number 75% of the time. What is the probability of getting 5 correct numbers, if you call the operators 8 times? Can you please help me with instructions on setting the formula up and maybe a simpler way for me to grasp the subject. Thank you Fatimah Sabb \n" ); document.write( "
Algebra.Com's Answer #445111 by stanbon(75887)\"\" \"About 
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The question is Assume that phone operators give out the correct number 75% of the time. What is the probability of getting 5 correct numbers, if you call the operators 8 times? Can you please help me with instructions on setting the formula up and maybe a simpler way for me to grasp the subject.
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\n" ); document.write( "# of ways to get 5 correct in 8 calls: 8C5 = (8*7*6)/(1*2*3) = 56
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\n" ); document.write( "Note: each of those 56 patters of 5 correct and 3 incorrect has
\n" ); document.write( "probability 0.75*5*0.25^3 = 0.2373*0.0156 = 0.0037
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\n" ); document.write( "Since each of the 56 correct/incorrect patterns are mutually exclusive
\n" ); document.write( "you have to add their probabilities to get:
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\n" ); document.write( "P(5 correct in 8 calls) = 56*0.0037 = 0.2976
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\n" ); document.write( "Note: I've shown you all the pieces. the answer is
\n" ); document.write( "usually written as follows:
\n" ); document.write( "p(x = 5 out of 8) = 8C5*(0.75)^5*(0.25)^3
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H. \n" ); document.write( "
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