A mosquito is walking at random on the nonnegative number line. She starts at $1$. When she is at $0$, she always takes a step $1$ unit to the right, but, from any positive position on the line, she randomly moves left or right $1$ unit with equal probability. What is the expected number of times the mosquito will visit $0$ before the first time she visits $4$?

The expected number of times is 4.

Step-by-step explanation:

Looking at the question, we see that this follows a geometric distribution because it is asking for the expected number of trials hat will bring about the FIRST SUCCESS. The probability of success is

Since it is a geometric distribution, we know that the expected value of a random variable X, E(X) that follows a geometric distribution is given as:

E(X) = 1/p where p is the probability of success.

Therefore, the expected number of times will be

E(X) = 1/(1/p) = 1/(1/4) = 4.

Hence, the expected number of times is 4.

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step-by-step explanation: