How to Use the Negative Binomial with NEGBINOM.DIST in Excel

Use NEGBINOM.DIST to estimate how many tries it takes to reach a target number of successes — like hires from interviews.

You will learn to

• Find the chance of exactly k failures before the target
• Find the chance of at most k failures
• Convert a total-attempts budget into failures

How it works

The negative binomial distribution answers "how many failures before I reach my target number of successes?" — interviews before filling 3 roles, sales calls before 5 deals, attempts before passing a test. NEGBINOM.DIST takes the number of failures, the number of successes you need and the chance of success on each try.

With cumulative TRUE it returns the chance of that many failures or fewer. To answer "within N total attempts", convert attempts to failures first: failures = N − successes needed.

=NEGBINOM.DIST(5,3,0.25,FALSE)