# SERM Appendix Mu/f'c*bd^2 vs Table in PCA Notes 08 Different?



## kalare (Oct 18, 2014)

I was working through NCEES sample exam problem 603 and could not get the SERM table to give the same answers as the sample exam when calculating the "w" factor to find rho. After much frustration I pulled out the PCA notes and found the similar table (page 7-3 for those that have the book) and the table is different and answers found using this table will match NCEES exam.

My question is...why are the different?! I used the SERM table throughout the PPI sample and got correct answers, but with NCEES sample exam it apparently doesn't work. I would assume using the PCI notes table would be the safe bet (or hand calculating rho...which takes much longer) but I'd like to understand why they are different and confirm which table I should be using on the test.

Anyone else come across this? Any ideas?

Thanks


----------



## Andy Lin (Oct 22, 2014)

Table in PCA was calculated including "φ" where as the table in SERM does not include "φ". However, the final "ω" stays the same regardless whichever one you use as long you are consistent.

For example, problem 603:


Using PCA (same as the solution): Mu/(*φ*f'cbd2) = 0.028 =&gt; ω = 0.029.
Using SERM: Mu/(f'cbd2) = 0.0256 =&gt; ω = 0.029.
So the results are the same.


----------



## kalare (Oct 22, 2014)

Ahhhhh, makes sense. Thanks for the clarification!


----------

