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Hello Team,

I’m curious if I could create the brand-price trade off question in LS. I have 4 brands, A, B, C, D and let’s say 5 price levels. In the first question the respondent is presented with the four brands, each with the same price level, eg. 1 euro. After choosing the preferred brand, the next screen shows the same four brands, but the chosen brand has increased price, let’s say 2 euro. The other brands prices stay at the same level as in the first question. In the next questions the price of the previously chosen brand increases.

My idea was to create a set of pictures for each brand showing the name and the price (five pictures for each brand, A01, A02, A03…, B01, B01…). The pictures would be in headers in the array questions. The pictures would have names with consecutive numbers, A01.png, A02.png,… and will be shown depending on the brand chosen in the preceding question. But this only idea and I see that I cannot convert into the solution in LimeSurvey. I'll be grateful for your comments and possible hints how to solve it.

Thank you for your help.
Elzbieta

I’m attaching the illustration of first 3 questions and .lss file as well as images archive. 

elissa wrote:

But this only idea and I see that I cannot convert into the solution in LimeSurvey. I'll be grateful for your comments and possible hints how to solve it.
 

What is the first issue you are not able to solve?  I haven't invested any thought in implementing BPTO in LimeSurvey cause I don't believe in the method. Choicebasedconjoint needs more work, but wastes only a bit more interview time than BPTO.

Not sure we have only one BPTO concept. When one brand reaches the upper price limit, will it be eliminated in the next round and the other three brands will be shown?
And you usually have a none-option, right? And only one question per page?
A lot of work in LimeSurvey, but what do you see as an technical issue unsolvable at first sight?
 

Thank you jelo. I'm not very much attached to this idea, so if it requires a lot of work, I will use other methods. I thought that it could be technically presented in such a way that the next question will show a picture with a number one price level higher in the picture file name than in the previous question for the chosen brand and the same pictures as in the previous question for the rest brands. And I thought it could be achieved by some expressions in the array headers but maybe this is completely wrong direction.

elissa wrote:

I'm not very much attached to this idea, so if it requires a lot of work, I will use other methods.
 

As long as we have no looping for questions/questiongroups the implementation effort will be high in LimeSurvey.
Other survey tools offer BPTO as question type with wizard. Same as with GaborGranger  and Choicebasedconjoint.

The behaviour would be like this, right?

B1P1 B2P1 B3P1 B4P1 None
Brand1Price1 chosen.

B1P2 B2P1 B3P1 B4P1 None
Brand1Price2 chosen

B1P3 B2P1 B3P1 B4P1 None
Brand2Price1 chosen

B1P3 B2P2 B3P1 B4P1 None

And that could go on for a while. 
The most extreme answer pattern would be to change a brand at the highest pricelevel.
Then that brand has to be removed from the answer set and other brands can be selected.
If you only switch the brand at the highest privelevel and don't select none, it could continue till the last brand has reached the highest pricelevel.


 

Hi,
here a rough idea how to do it with some expressions.

 

   

 



As @jelo,
there is one question and one equation for each level. So how many question are you going to ask?

Joffm

Joffm wrote:

As @jelo,
there is one question and one equation for each level. So how many question are you going to ask?
 

A BPTO without none option is not working. It would mean , that you always buy no matter what price.
Pricelevel need to be provided till above the market level of all brands.

Take a look that this demo
www.iqsn.de/L10/cawi/BPTO_Kredit/1/EN.php

 

It was just an example to show the equations.
It's easy to add a "None".
Oh, I saw that it starts again with a lower initial price.

This will be really difficult, because of the missing loops.
But could be possible with something like a main survey - subsurvey structure.
Where the subsurvey is called for each new round

Tomorrow afternoon.
 
Joffm 

Joffm wrote:

Oh, I saw that it starts again with a lower initial price.
 

Where does it start again with a lower price?
Four brands. Each selection means just rising the pricelevel of that brand. If one brand reaches the top pricelevel then it will be removed in the next question.
No brand has the price level reduced in the taskset. It stays the same or is rising.
The sheer amount of tasks is a lot of work. LimeSurvey isn't made for choice experiments. The mobile view of these choice tasks is often not good.

bugs.limesurvey.org/view.php?id=11292
 

Where does it start again with a lower price?

In the IFAD example.
Initial price is 50000 for all.
Select one and its price is raised by 10000.
Select 'none' and the already selected brands don't appear again and the new initial price is 40000.
Select 'none' again and the prise of all is lowered again by 10000.

Joffm 

Thanks, haven't check that. I would ignore lowering prices for a possible LimeSurvey implementation.

Start with prices way below the market median and then just rise prices. No need to allow people to lower prices again.

Not sure if it's worth the effort at all. The BPTO question type is making people angry. And it is exaggerating the importance of pricing. Sometimes adding decoy items into the task is helping a bit.

Personally I cannot recommend doing pricing studies with BPTO question types.
I cannot provide a modern approach for LimeSurvey cause LimeSurvey is lacking the functionality. If the sample size is high enough, I would consider a monadic approach.
A choice based conjoint analysed via hierarchical Bayes is still the gold standard. But you will need a different software.

Thank you both very much. Also, for the interesting discussion. I agree that this is not a perfect method but I my friend needs it for a small study. It will rather be used as a supporting tool, not the decisive one.

The solution suggested by Joffm at the beginning will work for my needs so thank you Joffm very much.