Excel Addin
Last saved 01/06/08
Excel Addin for Mac OSX (Should also be compatible with Windows)
Last saved 1/07/08

For Windows2000 WindowsXP:
Save the linked file above to
C:\Documents and Settings\CurrentUser\Application Data\Microsoft\AddIns
where the CurrentUser is the user name used to log on to the computer.

For Mac OSX

Save the linked file to:
Applications -- Microsoft Office X -- Office -- Add-Ins

Choose Tools --> Add-Ins... from the menu in Excel and check the box next to Fisherexact as shown below.

Update: 4/23/05

The function is FET(Group1[+], Group1[-], Group2[+], Group2[-], Optional Flag for 1 or 2-tailed )
The function can be called in Excel using the syntax in a cell as shown below:

=fet(A1, B1, C1, D1, True=1-tailed ) <-- Cell references
Standard Excel drag and drop, copy and fill should apply.

Update: 1/06/08

=fetl(A1, B1, C1, D1) -- Calculates the left side 1-tailed p-value
=fetr(A1, B1, C1, D1) -- Calculates the right side 1-tailed p-value[5,6]

Results of calculations for Fisher's Exact Probability

Group 1 Group 2 P-Value (1-tailed) P-Value (2-tailed)
No. + - + - SPSS EPI-INFO CalcFisher Excel Add-in Web Calculator [3] Excel Add-in
1 1 9 8 2 0.003 0.0027 0.0027 0.0027 0.0055 0.0055
2 0 7 3 6 0.15 0.15 0.15 0.1500 0.2125 0.2125
3 3 7 8 1 0.015 0.0149 0.0149 0.0149 0.0198 0.0198
4 5 4 2 7 0.167 0.1674 0.1674 0.1674 0.3348 0.3348
5 2 6 5 5 0.278 0.2783 0.2783 0.2783 0.3665 0.3665
6 4 6 7 3 0.185 0.1849 0.1849 0.1849 0.3698 0.3698
7 8 1 4 5 0.066 0.0656 0.0656 0.0656 0.131 0.1312
8 500 450 350 400 NP NP 0.0083 0.0083 NP 0.0167
9 1000 900 850 900 NP NP 0.0078 0.0078 NP 0.0156
10 2850 3000 2150 2100 NP NP 0.0332 0.0332 NP 0.0637

Update: 01/04/08

NP, Not possible
Table from Reference [1] with exception of Excel Addin column, or otherwise cited.

Additional test calculations for Fisher's Exact Probability based on feedback of software performance issues

Group 1 Group 2 P-Value (1-tailed) P-Value (2-tailed)
No. + - + - Web Calculator [3] Excel Add-in Web Calculator [3] Excel Add-in
1 5 20 5 15 0.48101 0.48108 0.731035 0.731035
2 5 15 5 20 0.48101 0.48108 0.731035 0.731035
3 5 5 15 20 0.48101 0.48108 0.731035 0.731035
4 5 5 20 15 0.48101 0.48108 0.731035 0.731035
5 5 20 15 5 0.00028 0.00028 0.000310 0.000310
6 280 270 3474 4457 NP 0.00071 NP 0.001375
7 260 270 3474 4457 NP 0.01058 NP 0.018831

References used during creation and testing:
1) A visual Basic Software for Computing Fisher's Exact Probability, Haseeb Ahmand Khan, http://www.jstatsoft.org/v08/i21/Article-JSS.PDF
2)http://bmj.bmjournals.com/collections/statsbk/9.shtml
3) http://www.psych.ku.edu/preacher/fisher/fisher.htm
 4) http://mathworld.wolfram.com/FishersExactTest.html
5)Fisher's Exact Test Created by Øyvind Langsrud http://www.matforsk.no/ola/fisher.htm
6) http://www.uoregon.edu/~robinh/lec_05a.txt

Questions or Comments: software@obertfamily.com

Software list

Changes to this page:
01/06/08:
New excel addin source provided
     1)  Added ability to calculate left and right side p-values (Thanks to Walter Park)

01/04/08:
New excel addin source provided
     1)  Fixed bug that occurred when lowest value in table was not unique (Thanks to Randy Johnson)
     2)  Fixed bug that included some combinations with P values greater than the critical value (Thanks to Walter Park)
Updated link to reference #3
Added 2-tail values to table and added second table based on user feedback

04/23/05:
New excel addin source provided
     1)  Fixed bug in variable declaration
     2)  Added ability to calculate both 1- and 2-tailed probabilities
     3)  Added file compatible with Mac OSX