Negative Binomial Distribution

The Negative Binomial distribution describes the distribution of the number of failures in order to achieve a specified number of successes, with a specified probability of success for each attempt. As such, by definition, it is dimensionless. It is frequently used in actuarial models.

The distribution requires two inputs, the Number of Successes (which must be a dimensionless positive integer) and the Probability of Success. Like the Poisson distribution, the Negative Binomial is a discrete distribution consisting of only integer values.

Note: Since this is a discrete distribution, the PDF Probability Density Function. A function whose Y-axis can be interpreted as providing the relative likelihood that the value of a random variable would be equal to value specified on the X-axis. Hence, the dimensions of the Y-axis are the inverse of those of the X-axis (i.e., the probability per unit length of the X-axis). view does not actually display a probability density function. Instead, it displays a probability mass function.