document.write( "Question 61048: on a true/false test a student has no idea what the answers are to 3 of the questions so he guesses. What is the probability that he will guess correctly on all 3 questions? at least 2 times? \n" ); document.write( "
Algebra.Com's Answer #41969 by funmath(2933)![]() ![]() ![]() You can put this solution on YOUR website! on a true/false test a student has no idea what the answers are to 3 of the questions so he guesses. What is the probability that he will guess correctly on all 3 questions? at least 2 times? \n" ); document.write( "There's 1 write answer out of two choices for each question. Therefore there's a \n" ); document.write( "Percetagewise that's 12.5%. Note that that's the same probability of getting them all wrong (think about it.). \n" ); document.write( "At least two right is 2 out of three and 3 out of three \n" ); document.write( "There are three ways to get 2 right (wrr),(rwr),(wrr) and one way to get them all right (rrr) \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "You can use binomial probability for this, but it would only be easier to do for a problem this small if you have a capable calculator. If you have a TI-83 or 84. Just hit, binomialpdf(3,.5,2)+binomialpdf(3,.5,3)=.5 or 1/2. \n" ); document.write( ": \n" ); document.write( "The formula for binomial probability is: \n" ); document.write( " \n" ); document.write( "P(x)=probability of x \n" ); document.write( "n=number of trials \n" ); document.write( "x=number of successes \n" ); document.write( "p=probabillty of success \n" ); document.write( "q=1-p=probabilty of failure \n" ); document.write( "For the probability of 2 correct answers: \n" ); document.write( "n=3, x=2, p=1/2=.5, q=1-1/2=.5 \n" ); document.write( "For the probabilty of 3 correct answers: \n" ); document.write( "n=3, x=3, p=.5, q=.5 \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "Happy Calculating!!! \n" ); document.write( " |