How to Use Excel's Combin Function

By eHow Computers Editor

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Excel's Combin function returns the number of ways that the specified number of items can be combined. It may be used to determine the maximum number of groups for a given number of items. The following steps will show how to use Excel's Combin function.

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Instructions

Difficulty: Moderate

Step1

Learn the syntax for Combin. It is Combin (number,group_size) where number is the number of items and group_size is the number of items in each group.

Step2

Study how arguments for Combin are used. Numeric arguments will be truncated if needed to provide integers. Combin will return #Num! if either argument is negative or if number < group_size. Any non-numeric argument will cause Combin to return #Value!.

Step3

Understand how a combination is defined by Combin. A combination is any set of items and does not consider their order as a permutation does.

Step4

Examine the way Combin calculates its result. The following standard mathematical formula is used: n!/k!(n-k)! where n is the total number of items and k is the number of items in each group.

Step5

Look at a simple example of Combin: Combin (8,2)=28. Check the result with the equation given in Step 4: n!/k!(n-k)! = 8!/2!(8-2)! = 40,320/2x720 = 28. There are 28 different ways to combine eight items into two groups.

Step6

Use some slightly more complex examples to see how Combin works:

Combin ("2",2) = 1. Note two things about this formula. First, the text "2" is implicitly converted to the numeric value 2. Second, our equation gives 2!/2!(2-2)! = 1 because 0! is defined as 1.