The NEGBINOM.DIST function returns the negative binomial distribution, the probability that there will be a given number of failures before a required number of successes is achieved.
For example, you need to find 10 people with excellent reflexes, and you know the probability that a candidate has these qualifications is 0.25. NEGBINOM.DIST calculates the probability that you will interview a certain number of unqualified candidates before finding all 10 qualified candidates.
 This function was introduced in Excel 2010 and so is not available in earlier versions.
 The NEGBINOM.DIST function replaces the NEGBINOMDIST function included in earlier versions of Excel.
Syntax
=NEGBINOM.DIST(number_f,number_s,probability_s,cumulative)
Arguments
Argument  Description  

number_f  The number of failures encountered before number_s successes  
number_s  The required number of successes  
probability_s  The probability of success in one trial  
cumulative  A logical value that determines the form of the function

Examples
A  B  C  D  

1  Data  Description  
2  10  Number of failures  
3  4  Threshold number of successes  
4  0.25  Probability of a success  
5  
6  Formula  Result  Notes  
7  =NEGBINOM.DIST(A2,A3,A4,TRUE)  0.47866  Cumulative negative binomial distribution for the terms above  
8  =NEGBINOM.DIST(A2,A3,A4,FALSE)  0.062913  Probability negative binomial distribution for the terms above 
Common Function Error(s)
Problem  What went wrong  

#VALUE!  Occurs if either:


#NUM!  Occurs if either:

The binomial distribution is a statistical measure frequently used to indicate the probability of a specific number of successes occurring from a specific number in independent trials.
The negative binomial distribution calculates the probability of a given number of failures occurring before a fixed number of successes, i.e. the number of successes is fixed and the number of trials varies.
The following two forms are used:
 Probability Mass Function – calculates the probability of there being exactly f failures before s successes
 Cumulative Distribution Function – calculates the probability of there being at most f failures before s successes.
The equation for the negative binomial distribution is:
where, x is number_f, r is number_s, and p is probability_s.
See Wikipedia for more information on negative binomial distribution.