# Interpolation with part worth utilities in Excel simulator

I have conducted a CBC study and estimated HB part worth utilities with LightHouse Studio. I am now building an Excel simulator and would like the Excel simulator to do linear interpolation between price levels tested in conjoint. For example, in conjoint we tested price levels: \$2, \$4, \$6. In my Excel simulator, I want to be able to evaluate preference share for \$4.50 which was not tested in conjoint/does not have a part worth utility from CBC HB.

My Excel simulator creates a design vector for each simulated product with value=1 for attribute levels selected for a product and value=0 for attribute levels not selected for a product. This is then multiplied by the utility vector using the SUMPRODUCT() formula to obtain Total utility for each simulated product. The 1/0 coding works for non-interpolated values BUT how do I code the design vector for interpolated values? For example, is this the correct way to code the design vector for \$4.50?

Step 1. Proportion of utility range for \$4.50: (\$4.50-\$4)/(\$6-\$4)=0.25.
Step 2. Price attribute design vector (0, 0.75, 0.25) to be multiplied by utility vector:
\$2=0
\$4=(1-0.25)=0.75
\$6=0.25

Thank you.
answered Aug 5, 2019 by Gold (20,130 points)