
question about calculating odds
Sorry, this isn't an ASP question, but it is for a game I am working on and thought someone could help. <BR><BR>I used an online calculator to determine the following and want to verify if it is correct but am not too good with odds:<BR><BR>I have a 1 in 10 chance of matching a number. If my number is a match, I have a 1 in 130 chance of picking a winning number. What are my odds of picking the winning number? <BR><BR>Using this calculator, http://www.csgnetwork.com/oddscalc.html, it says the combined odds are 1 in 9730. Can anyone help verify this?

RE: question about calculating odds
oh, one more thing. What if I am presented with the 1 in 10 chance 7 times and each time that I made a match, I would increase my odds of picking a winning number  i.e. instead of 1 in 130, it would be 1 in 129 and then 1 in 128? <BR><BR>I could really use a formula for this :)

RE: question about calculating odds
I think you need to describe this a little better. The way you originally described it (1 in 10 then 1 in 130), you're odds would be 1 in 1300. The odds of either event are not affected by the other so you simply multiply the odds of each action The odd of flipping a coin and getting heads (1/2) and then rolling a die and getting 6 (1/6) would be 1/2 * 1/6 = 1/12.<BR><BR>The case you're describing here is more complicated because the odds of the second event depend on the outcome of the first. You could figure out an answer, but ugh.. it's a lot tougher.

yes, its ugly
yes, the odds of the second event do depend on the outcome of the first. <BR><BR>thanks for your input, i guess i will need to sit down and crack open a stats book or something :)

Bernouli Trials
I think you have to consider all the possible outcomes of the 7 chances. 0 mathces, 1 match... 7 matches. Then multiply the odds of the first event by the odds of the second.<BR><BR>(odds of 0 matches) * 1/130 (odds of 1 match * 1/129) ...<BR><BR>There's a binomial distribution equation that will give you the odds of getting exactly X mathces in 7 tries (Your first event!) (http://mathworld.wolfram.com/BinomialDistribution.html)<BR><BR>Not sure what you do with all these results though. Add them up maybe? Bill might want in on this.

RE: Bernouli Trials
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