Please help me is this statistical problem.
An urn contains black and white balls. A sample of size n is drawn with replacement. What is the maximum-likelihood estimator of the ratio R of black to white balls in the urn?
Suppose that one draws balls one by one with replacement until a black appears.
Let X be the number of draws required (not counting the last draw).
This operation is repeated n times to obtain a sample X1, X2, ..., Xn.
What is the maximum-likelihood estimator of R on the basis of this sample.