Talk:"Ancient Japan's Got Talent!"/@comment-50.9.230.229-20131127072024/@comment-24122694-20131127090630

The chance to get a 5* remains the same for all 30 days. Alternatively:

Let X be the random variable of getting a 5* in 30 rare summons. X ~ B (30, 0.0153)

Since n = 30 is large, and np = 0.0153 * 30 = 0.459 < 5,

X ~ Po (0.459) approximately.

This means you will get 0.459 5* card in 30 tries... unless you don't consider 30 to be sufficient large, then the approximation to Poisson distribution wouldn't work. XD