The among groups SS is the sum across all N cases of [(Mean of the group the score is in) - (Grand Mean)]**2. Since this SS is constant across cases within a group, you simply multiply it by the group n and then sum those products across groups. Yes, you could weight the groups differently, for example, using the harmonic mean sample size instead of individual group sample sizes.
Cheers, Karl W. -----Original Message----- From: Marc Carter [mailto:[email protected]] Sent: Wednesday, February 22, 2012 8:57 AM To: Teaching in the Psychological Sciences (TIPS) Subject: [tips] Dumb question.... Hi, all -- I fear this to be a really stupid question, but... In ANOVA, why are the squared deviations in the SS between groups scaled (multiplied) by _n_? I was once told it was to weight them, but that somehow doesn't seem right. Can someone help? TIA, marc The information contained in this e-mail and any attachments thereto ("e-mail") is sent by Baker University ("BU") and is intended to be confidential and for the use of only the individual or entity named above. The information may be protected by federal and state privacy and disclosures acts or other legal rules. If the reader of this message is not the intended recipient, you are notified that retention, dissemination, distribution or copying of this e-mail is strictly prohibited. If you have received this e-mail in error please immediately notify Baker University by email reply and immediately and permanently delete this e-mail message and any attachments thereto. Thank you. --- You are currently subscribed to tips as: [email protected]. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13060.c78b93d4d09ef6235e9d494b3534420e&n=T&l=tips&o=16204 or send a blank email to leave-16204-13060.c78b93d4d09ef6235e9d494b35344...@fsulist.frostburg.edu --- You are currently subscribed to tips as: [email protected]. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13090.68da6e6e5325aa33287ff385b70df5d5&n=T&l=tips&o=16214 or send a blank email to leave-16214-13090.68da6e6e5325aa33287ff385b70df...@fsulist.frostburg.edu
