## Friday, August 31, 2012

### How To... Calculate the Factorial of a Number in Excel

Today I came across the exclamation mark symbol while preparing some notes for a statistics class on Probability. It has been a very long time (probably 1st year in College) since I came across or last used this symbol. When used with a number it means that it is the factorial of that number. For example:

5!  =  5 x 4 x 3 x 2 x 1  =  120

While this calculation can be done in your head, it is much more awkward to calculate the factorial of a larger number. So I decided to see if I could find an easy way to do it in Excel 2010, and sure enough it is relatively straight-forward to so using the FACT function. Here is my short video showing how to do this:

Today was also the first time that I had someone with me when I was recording a video. Normally I close the windows, turn my phone to silent, and put a Do Not Disturb note on the door. Up to now I have been on my own in a quiet office - I do not like company when recording. The Head of the School of Computing at NCI, Dr Pramod Pathak, expressed an interest in seeing how I made the recordings, so he was a welcome guest today. Having someone else beside you doing this is quite an experience. Of course I wanted the recording to be a good one and demonstrate an easy way to create educational material - but I also felt that I had to do a better job and not make any mistakes while being watched. Having someone present definitely  made me feel and perform differently.