+ Reply to Thread
Results 1 to 3 of 3

Thread: (weighted) mean of standard deviations

  1. #1
    Points: 1,039, Level: 17
    Level completed: 39%, Points required for next Level: 61

    Posts
    3
    Thanks
    1
    Thanked 0 Times in 0 Posts

    (weighted) mean of standard deviations




    Dear all,

    I have the following problem. Suppose I have three results of temperature measurements:

    10 +/- 2
    2 +/- 6
    9 +/- 3

    Here the +/- are the standard deviations, or uncertainties on the measurements. The average here is 7. I do not want a weighted average because lower temperatures have a larger error bar, and a weighted average would obviously skew the mean towards higher temperatures.

    Now, does anyone know a reasonable way to calculate the uncertainty on this average? I figure it is not simply the mean of the standard deviations, but unsure.

    Any help very much appreciated!

  2. #2
    TS Contributor
    Points: 22,410, Level: 93
    Level completed: 6%, Points required for next Level: 940

    Posts
    3,020
    Thanks
    12
    Thanked 565 Times in 537 Posts

    Re: (weighted) mean of standard deviations

    This depends on the information you have for your data.

    If you have the complete raw data/all sufficient statistics, then you can recalculate the pooled mean and standard error again.

    If you have the sample sizes for the three groups, there is also a nice discussion about this issue on how to work on the pooled sample variance. See

    http://www.talkstats.com/showthread....ard-deviations

  3. The Following User Says Thank You to BGM For This Useful Post:

    Kolin (11-22-2011)

  4. #3
    Points: 1,039, Level: 17
    Level completed: 39%, Points required for next Level: 61

    Posts
    3
    Thanks
    1
    Thanked 0 Times in 0 Posts

    Re: (weighted) mean of standard deviations


    Thank you so much, very much appreciated! The other discussion has everything I needed.

+ Reply to Thread

           




Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts






Advertise on Talk Stats