A survey from Teenage Research Unlimited found that 40 of te

A survey from Teenage Research Unlimited found that 40% of teenage consumers receive their spending money from part-time jobs. If nine teenagers arc selected at random, find the probability nat at least two of them will earn their spending money from part-time jobs. 0.9295 0.83 0.0705 0.I7

Solution

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 = 0.9295 [ANSWER, A]