Negative Binomial Distribution
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Tap a term to see what it means, or .
Calculate
Example: a salesperson closes a deal on 20% of calls. What is the chance that the day's 3rd sale comes exactly on the 10th call? Change the values to work out your own case.
Step by step
What each term means
- Probability (P(X = k))
- The chance that success number r happens exactly on trial k, with k = r, r + 1, …
- Positions of the Other Successes (C(k − 1, r − 1))
- Trial k must be a success; the other r − 1 can be in any of the k − 1 earlier trials.
- Successes (pʳ)
- The chance of r successes, each with probability p, in independent trials.
- Failures ((1 − p)ᵏ⁻ʳ)
- The chance of the k − r failures along the way.