# What is the moment generating function of a geometric distribution?

## What is the moment generating function of a geometric distribution?

The something is just the mgf of the geometric distribution with parameter p. So the sum of n independent geometric random variables with the same p gives the negative binomial with parameters p and n. for all nonzero t. Another moment generating function that is used is E[eitX].

### What is the moment generating function of binomial distribution?

The Moment Generating Function of the Binomial Distribution (3) dMx(t) dt = n(q + pet)n−1pet = npet(q + pet)n−1. Evaluating this at t = 0 gives (4) E(x) = np(q + p)n−1 = np.

#### What is the probability generating function of geometric distribution?

The Geometric Distribution The set of probabilities for the Geometric distribution can be defined as: P(X = r) = qrp where r = 0,1,… By (6.2), E(X) = q p. Both the expectation and the variance of the Geometric distribution are difficult to derive without using the generating function.

Is binomial distribution the same as geometric distribution?

Binomial: has a FIXED number of trials before the experiment begins and X counts the number of successes obtained in that fixed number. Geometric: has a fixed number of successes (ONE…the FIRST) and counts the number of trials needed to obtain that first success.

How to find the moment generating function of a binomial distribution?

Then its moment generating function is Can someone please explain how the sum is obtained from lines (2) to (3)? p(t) = E(etk) = n ∑ k = 0(n k)pk(1 − p)n − ketk = n ∑ k = 0(n k)(pet)k(1 − p)n − k = (pet + (1 − p))n The last step is simply an application of the binomial theorem.

## How to calculate the mean of the moment generating function?

You will see that the first derivative of the moment generating function is: M ’ ( t) = n ( pet ) [ (1 – p) + pet] n – 1 . From this, you can calculate the mean of the probability distribution. M (0) = n ( pe0 ) [ (1 – p) + pe0] n – 1 = np. This matches the expression that we obtained directly from the definition of the mean.

### What should you know about binomial and geometric distributions?

In this lesson, we learn about two more specially named discrete probability distributions, namely the negative binomial distribution and the geometric distribution. Upon completion of this lesson, you should be able to: To understand the derivation of the formula for the geometric probability mass function.

#### Which is the mass function for a binomial distribution?

Start with the random variable Xand describe the probability distributionmore specifically. Perform nindependent Bernoulli trials, each of which has probability of success pand probability of failure 1 – p. Thus the probability mass function is f(x) = C(n, x)px(1 – p)n- x