aarthrj3811 said:
Now you have to remember that all Dowsing is the same as guessing.The only question here is HOW MANY COINS WILL I FIND?
Hey xupz....So the Question is to hard for you?
Art it's already been answered, you sum the probabilities from the binomial distribution just as Carl has already shown. Here I'll break it down for you even more because you obviously have some kind of patronizing manner as if you think this question is too hard to figure out (when in reality I first learned all the basic discrete probability distributions in my VERY FIRST INTRO PROB STATS CLASS). If you're looking for a number, if you ran this test an infinite number of times it will average out 1 correct guess. That is the expected number of coins on average you'll guess correctly. See my work below to PROVE it.
Now since you're such the math wizard, I'll break it down for you using the binomial distribution:
Y~Binomial (n, p) where by definition of the binomial distribution you have 4 conditions:
1) n fixed trials
2) each trial is success or failure
3) probability of success is fixed (in this case .10)
4) trials are independent (which they are)
The equation is:
P(y) = (n C y)*p^y*(1-p)^(n-y) where
n C y is choose
y = # of successes (0->10)
p = probability of success (.10)
n = number of trials (10)
The expected value of you guessing correctly is mu = np = 10*.10 = 1.
Now let's do some actual plugging and chugging:
P(y=0) = (10 C 0)*(.10)^0*(1-.10)^(10-0) = 1*1*(.90)^10 = .34867 or 34.867%
This is the probability that you guess EXACTLY ZERO correct.
P(y=1) = (10 C 1)*(.10)^1*(1-.10)^(10-1) = 10*(.10)*(.90)^9 = .38742 or 38.742%
This is the probability you guess EXACTLY ONE correct.
etc for y= 0 to 10
Now if asked you what's the probability that you guess at least 1 correctly then it's basically summing all the probabilities from 1->10 and removing zero. Since we already know the probability of you guessing zero correctly, all we have to do is subtract the probability of zero correct guess from 1 (the sum of all probabilities for all guesses) and you get 1- .34867 = .65133 or 65.133% probability of guessing AT LEAST 1 correctly.
Now Art, is this too hard for you to understand?