Exporting ACBC Data to .CHO File

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Some researchers may wish to export the data to a .CHO file for analysis using other software programs, such as our CBC/HB system or Latent Class software. (Notes: our market simulator cannot import a .CHO file from an ACBC study correctly, as the new .CHO file includes additional incompatible information.  If your design uses constructed lists that drop entire attributes from consideration, please see the warning further below.)


1. Select File | Data Management


2. Select the Export Data tab


3.  Add a new export job by clicking Add Job... (name your job something like ".CHO export")


4.  Click Add to add a new Export action.  Select the ACBC (.cho, .att) type.


5.  If you have more than one ACBC exercise within your Lighthouse Studio project, select which ACBC exercise to export.


6.  If you used constructed lists to drop certain levels of certain attributes for some respondents, select Settings and specify how the dropped levels should be treated.


7.  Click OK to finish adding the new job to the export list.


8.  From the Data Management dialog, Export Data tab, click Export Jobs (make sure the jobs you want exported are checked within the list).


When you export a .cho file, ACBC reports how many respondents have been exported to the file.  It also informs you regarding which attribute numbers in the .cho file are coded as "user-specified."  This simply means that these columns in the .cho file should be used in the estimation software "as-is": they require no further effects-coding or dummy-coding.  When you open the .cho file within our CBC/HB or Latent Class software, you should change the coding method for these attributes to "user-specified."  The "user-specified" columns within ACBC studies reflect the Summed Price attribute, the None parameter, and any threshold parameters for attributes using constructed lists (where selected levels were dropped from consideration).


Under the Settings dialog, you can select which respondents to export as well as the method to use for respondent numbering.


You can also select which tasks to include in the .CHO file: BYO (by attribute), Screener Section, Choice Task Tournament.


Scaling of Summed Price


The default prior settings in CBC/HB software work well as long as the data are scaled similarly within the design matrix.  Generally, attributes are effects-coded, which transforms the level indices to values of 1, 0 or -1.  But, if your summed prices are in the hundreds, thousands or millions, it can pose serious problems for proper convergence in CBC/HB.  Thus, the software allows you to rescale your price units by supplying a price multiplier on the Settings dialog.  We recommend a price multiplier that brings your summed prices into units scaled in the 1s or 10s.  For example, a price range of 1 to 5 or 10 to 50 seems to work well.  But, prices scaled from 100 to 500 or especially 100,000 to 500,000 would not work well.


Please note that if using summed prices, your results when using CBC/HB to estimate utilities will not exactly match the results from running HB within the ACBC interface.  That is due to the way we have chosen to rescale price in ACBC to ensure proper convergence under unpredictable price scaling conditions.  Within the ACBC interface, HB automatically transforms prices to a -1 to +1 range within the design matrix.  Then, before writing the results out to the utility file, it scales the utilities back to the original price scaling.  Using a .cho export, however, will result in prices that are not zero-centered.  This will especially affect the constant (the None parameter) in the model.


How to Treat Missing Levels


If you used constructed lists for some attributes, we recognize that it is possible that respondents have some levels deleted prior to the ACBC interview.  For example, you may have deleted certain brands that were unacceptable or not available to the respondent.  You must specify how to treat these levels in the coding of the .cho file.  Missing levels can be treated as:


Inferior to included levels


Missing at random


This parallels the options that are available within the built-in estimation interface for HB within the ACBC system.  If you specify that missing levels are to be treated as inferior to included levels, additional choice tasks are written to the file for each respondent, informing utility estimation that included levels are superior to (chosen over) inferior levels.  If you specify that missing levels are either Unavailable or Missing at random, these additional tasks are not written.  The result is the same for the .cho export whether you select these latter two options.


Warning Regarding Using .CHO File and Missing Attributes


If you used constructed lists to drop certain attributes from the ACBC questionnaire that were deemed entirely unimportant (using questions prior to the ACBC sections), then you should be careful about using CBC/HB, Latent Class, Aggregate Logit or another routine outside ACBC software for estimation. Unless you take special steps to inform utility estimation that certain attributes have been dropped and should have no importance for certain respondents, your utility estimation will overstate the importance of such attributes that were dropped from consideration. ACBC's built-in CBC/HB and Monotone Regression routines inform utility estimation regarding missing (and entirely unimportant attributes) by inserting utilities of zero for the levels of such attributes for respondents who have dropped the attribute from consideration in ACBC.  Therefore, if you use another routine, you should take steps such as post-processing the utilities to set the part-worths (at the individual level) to zero for any attributes that have been dropped from consideration by those respondents.

Page link: http://www.sawtoothsoftware.com/help/lighthouse-studio/manual/index.html?exportingacbcdatato_chofi.html