Whats the formula for variance between batches?

[Fat Ryan]

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 I've looked in my book, notes, and Google. I am getting nothing here :/

 

[Fat Ryan]

any1?

 

[hhn2002]

keep in mind I am 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 can't 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.

 

[brewnog]

If you really expect help within 35 minutes of posting your question, you're in the wrong place.

 

[Fat Ryan]

hhn, thanks for the help. i ended up getting help from another grad student before i could even get back to my computer though. thanks for your time though.