text: anyone know probability well? i take online surveys.  for each one i take, i get entered into a sweepstakes. i'm not sure what my odds are, let's just say 1:1000.  my question is: do my odds of winning go up with each survey i take, or are my odds always the same, starting over each time? a good analogy here is flipping a fair coin.  so like if you have flipped a coin 5 times and each time came up heads.  what is the probability that the 6th time will be heads as well?    answer: the same as it was the 1st, 2nd, 3rd... 50/50.  each event is independent of every other event, so the probability is always the same for each individual event.    now, if you flip 6 coins simultaneously, and you want to know what the probability of getting at least one head then you use the binomial distribution formula:    b(k;n,p) = (n choose k)(p^k)(1-p)^(n-k)  where n = the total number of possible outcomes and k = the amount of desired outcomes and p = the probability of k occurring and 1 - p = the probability of k not occurring  note: "n choose k" is found using the general formula (n!/[(n-k)!k!] which is like...well say n =5 then n! is 5x4x3x2x1 (in the numerator) and say k = 3 then the denominator is (2x1)(3x2x1).    is that clear as mud?