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Whats the formula for variance between batches?

  1. Sep 14, 2009 #1
    Im working on a lab for my Civil Engineering Materials class and its asking for the "between batch variation" (SBB^2) for different cylinders of Portland cement concrete. Its not written anywhere on the lab sheet. And Ive looked in my book, notes, and Google. Im getting nothing here :/
  2. jcsd
  3. Sep 14, 2009 #2
  4. Sep 14, 2009 #3
    keep in mind im not studying to be a civil but mech engineer so this is the best i can come up with.

    heres a link to a digital book that discusses batch variations:
    http://books.google.com/books?id=g8...age&q=cement between batch variation&f=false"

    if you look at table 1.7 and read the page above it it seems as if S=compressive strength in MPa. so you are looking at the difference between compressive strength of both batches.
    absolute value of S(batch A)-S(batch B).
    maybe your making it harder than it seems when it might just be a trivial subtraction operation. and maybe that is why you cant find a formula to it because its that simple.
    anyways keep in mind this is not my specialty and i know absolutely nothing about civil but this is what i understood purely from the text.
    Last edited by a moderator: Apr 24, 2017
  5. Sep 14, 2009 #4


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    If you really expect help within 35 minutes of posting your question, you're in the wrong place.
  6. Sep 15, 2009 #5
    hhn, thanx for the help. i ended up getting help from another grad student before i could even get back to my computer though. thanx for your time though.
    Last edited by a moderator: Sep 16, 2009
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