X the number of successes it can take the values 0 1 2 3. This means that the probability of success p does not change from trial to trial. But there are a few other ways to look at the distribution that can be illuminating and also help interpret the case where r is not an integer.
Using the formula for p x you obtain the probabilities for x 0 1 2 and 3 red lights.
Formula If the random variable X is the number of trials necessary to produce r events that each have probability p then the probability mass function PMF of X is given by. To answer this question we can use the following formula in Excel. So X number of red traffic lights has a binomial distribution. A desired confidence.