Btw: Your chances for one or more red stamps is 40.5% if you ordered 50
Yes indeed, i got the same 1-(1-1500/150000)^50=0,405
That being said, the exact calculation involves the hypergeometric distribution. However i agree that,
in this case, the binomial distribution can be used instead.
Best regards
The only thing i am worried about this calculation is if its truly a random selection that they are offering to people.