12 1 point An undergraduate student believes that the probab
Solution
12.
P(A U B) = P(A) + P(B) - P(A n B)
=0.60 + 0.55 - 0.35
= 0.80 [ANSWER, D]
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13.
Note that P(at least x) = 1 - P(at most x - 1).          
           
 Using a cumulative binomial distribution table or technology, matching          
           
 n = number of trials =    9      
 p = the probability of a success =    0.4      
 x = our critical value of successes =    2      
           
 Then the cumulative probability of P(at most x - 1) from a table/technology is          
           
 P(at most   1   ) =    0.070543872
           
 Thus, the probability of at least   2   successes is  
           
 P(at least   2   ) =    0.929456128 [ANSWER, A]
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