Q. Exhibit 5-8 random variable x is number of occurrences of an event over an interval of ten minutes. A. at least 2 outcomes are possible b. probability changes from trial to trial c. trials are independent d. None of these alternatives is correct. Standard deviation of this binomial distribution is a. 20 b. 16 c. 4 d. 2 which of following is a characteristic of a binomial experiment? A. at least 2 outcomes are possible b. probability changes from trial to trial c. trials are independent d. None of these alternatives is correct.