I have a stats problem I cannot solve, I have the answer and I have attempted the question. I just need to know where I am going off track. Any assistance would be highly appreciated.
Q: What is the probability that a six-digit telephone number has no repeated digits? Do not allow the number to start with a zero.
So I know that there are 10 possible digits that can be selected, each time the pool of selected digits gets smaller.
The first digit cannot be zero therefore there are 9 possibilities for this digit. Then, seeing as the order doesn't matter, but repeats do, so I thought a permutation would be the correct method to apply.
9 * ((9!)/(9-5!)) = 136,080 (<-- total number of 6 digit numbers)
Without repeats and no 0 as first digit
Total number of 6 digit numbers = 10^6
Therefore the probability of this scenario happening is:
(139,080/10000000) = 0.13608
Did I make a mistake when using the permutation?