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How to get utilities for new price level (interpolated between existing levels) in SMRT?

I have done a CVA study with three attributes including Price. The price was described using four levels (0, 10, 25, 50).  Now I would like to interpolate between levels for price and check what happens if I have price, for example, 35.
There is nice and easy way to interpolate between levels in SMRT, but it shows me only simulation of market shares for new price level (35) and I would like also to see utilities for this level. How can I get SMRT to show me utilities for new price level (interpolated between existing levels)?

Many thanks in advance for help.
asked Oct 23, 2013 by Tomek

1 Answer

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Best answer
Since SMRT does a simple straight-line interpolation between the two nearest points, the solution is to figure out what % between $25 and $50 is your new value, $35.  It is $10 on the way along the $25-point range between $25 and $50, which is 40% of the way.  

So, let's say the utility reported in SMRT for level $25 is 80 and the utility of $50 is 40.  To compute the interpolated utility for $35, you multiply (1-0.4)(80) + (1-0.6)(40), resulting in 64 utiles.  

To double-check yourself, do a scatter plot of the three prices with their three utilities in Excel, and it should be a straight line.

Some people build their own simulators in Excel and the formula I just gave is the easy way to do the interpolation for computing the utilities at the individual levels for the raw utilities prior to summing the utilities across attributes (to obtain the total utility of a product concept) and exponentiating the utilities to obtain the Share of Preference per the Logit rule.
answered Oct 23, 2013 by Bryan Orme Platinum Sawtooth Software, Inc. (198,315 points)
Thank you very much. This solves my problem :)