Dear Sawtooth Team,
I have a question regarding the linear attribute coding within the HB-estimation.
Imagine a CBC analysis that contains (besides other attributes) a price attribute having six levels with equal distances between the price levels.
The price levels are as follows: $0; $29.99; $59,99; $89.99; $119.99; $149.99.
I want to estimate a single utility coefficient for the price.
In order to meet the attribute coding guidelines, I made sure that the specified values metrically correspond to the quantities shown to respondents. Additionally the values have a magnitude of about single digits. Consequently, I coded them in the CBC/HB estimation settings as follows:
0; 0.2999; 0.5999; 0.8999; 1.1999; 1.4999.
However, I found that coding the attributes as zero centered values (i.e., -1.46, -0.88, -0.29, 0.29, 0.88, 1.46) seems to work better in terms of convergence.
I was wondering if that makes any sense. Especially since the helpfiles states that "CBC will automatically zero-center any values you specify when creating the independent variable matrix".
When aiming for linear coding, is there generally a benefit in zero centering price values for the attribute coding?
Thank you and best regards,
E.S.