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Standard Deviation in One Direction

  1. Nov 12, 2009 #1
    I need to calculate the average time of an event, and I'd like to calculate standard deviation as well. The problem is - there is no such thing as negative time - zero is a boundary - so how does it make sense if the average is 4000us (microseconds) and the stdev is 5000us?

    Is there a different measure that I should be using when there is a boundary on one-side, like some sort of a one-directional standard deviation? "Semi-infinite interval" comes to mind, and I Wikipedia'ed such probability distributions for more information, but I'm not sure what to make of it.

    Thanks in advance!
  2. jcsd
  3. Nov 12, 2009 #2


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    Do you have a distribution in mind that actually does that? Sometimes if the distribution is badly skewed the interquartile range gives a better description than the standard deviation.
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