Selection with Exactly One from a Particular Group

Selection with Exactly One from a Particular Group

## Formula

If exactly one object must be selected from a group of $$m$$ objects while the remaining $r-1$ objects are selected from the other $n-m$ objects:

$$m{}^{n-m}C_{r-1}$$

## Usage

- Used when exactly one member of a specified group must occur in the selection.