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June 26th, 2009, 02:05 AM  #1 
Newbie Joined: Jun 2009 Posts: 8 Thanks: 0  Standard Deviation
If the distribution of time that 5 employees commute to work is 10; 10; 10; 20; 20 minutes. What is the standard deviation of this population of employees? 
June 26th, 2009, 05:19 AM  #2 
Global Moderator Joined: Nov 2006 From: UTC 5 Posts: 16,046 Thanks: 938 Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms  Re: Standard Deviation
Again, where are you stuck?

June 26th, 2009, 05:51 AM  #3 
Newbie Joined: Jun 2009 Posts: 8 Thanks: 0  Re: Standard Deviation
so mean = 14 n=5 squaring the differences and summing after etc etc...i get 120. divide by 4 (n  1) and i get 30....so square root of 30 right? 
June 26th, 2009, 06:11 AM  #4 
Global Moderator Joined: Nov 2006 From: UTC 5 Posts: 16,046 Thanks: 938 Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms  Re: Standard Deviation
Looks good. That's the sample standard deviation, so appropriate if there are actually lots of employees and you chose 5. If these are all the employees, you divide by n instead of n1.


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