SOLUTION: Use a normal approximation to find the probability of the indicated number of voters. In this​ case, assume that 124 eligible voters aged​ 18-24 are randomly selected. Suppose

This problem is on Binomial distribution

    n = 124 total trials;  p = 0.22 is the probability of an individual success;

    k = 30 is the number of successful trials.


Since the number of trials is great, we use the normal distribution as an approximation.


The mean is  m = n*p = 124*0.22 = 27.28;  the standard deviation is  

    SD =  =  = 4.61285  (rounded).


Now you can use your calculator

    p = normalcfd( 29.5, 30.5, 27.28, 4.61285) = 0.0726  (rounded).    ANSWER


The numbers 29.5 and 30.5 come with the continuity correction.