# Multiple Price List Task (Time Preference (Patience))
Implementation of 2 MPL's Patience from [Camerer, C., Chapman, J., Snowberg, E., Dean, M. & Ortoleva, P. (2016). Design Document for Robust Econographics.](http://www.its.caltech.edu/~snowberg/WEP/design/WEP%20Robust%20Econographics%20Survey%20Document%20FINAL.pdf "Design Document for Robust Econographics") Part III.N 

This version differs slightly from the procedure described in the aforementioned publication. 
All deviations are explained transparently below. This App is conducted in German. Page sequence (MPL sequence) is randomized in in this app.

In all MPLs by Chapman et al. (2016), the distances between the amounts are not identical, but are smaller around the 
indifference point. In these implementations, the distances between the amounts are always kept identical 
(e.g., always 500 points). As a result, the length of the list may differ. 
The range in this app differs slightly to Chapman et al (2016): [0 - 4500] instead of [0 - 4100] and [0 - 6500] instead of [0 - 6100]. For details, check the options for each MPL listed below.

#### MPL 1:
- <b>Number of choices:</b> 10
- <b>A:</b> patient option: [4000] points in 30 days
- <b>B:</b> impatient option: [0, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500] points today<br>

#### MPL 2:
- <b>Number of choices:</b> 14
- <b>A:</b> patient option: [6000] points in 365 days
- <b>B:</b> impatient option: [0, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500] points today<br>

## Settings
No Settings needed.

## Exported Data
Variables are Structured as defined in the 'Synergia Measures Readme': `conceptcode_measure_item` (e.g. `timepref_pat_mpl_1_...`).
In the export file, there are the following variables for each Multiple Price List (`timepref_pat_mpl_1_...` - `timepref_pat_mpl_6_...`):
- `...count_patient_option`: Number of rows where the risky option was chosen
- `...count_impatient_option`: Number of rows where the safe option was chosen
- `...error`: Indicator whether a hint (error message) is was trigered during the MPL Decision (This Variable is only available, if Error Messages are provided by the above mentioned authors)
- `...choice_1` - `...choice_n`: for each decision, there is one variable that indicates, whether the `patient` or the `impatient` option was chosen

One of Options in one of the two MPLs is randomly selected for a potential payoff (`choice_to_pay`) and stored in the variable `self.participant.vars['mpl_pat_pot_payoff']`. This Variable can be selected with the MPL_Results App.

## Comparability
The content of the first two MPLs is similar to the Present Bias MPLs 1 / 2 (`timepref_pb_mpl_1_...` / `timepref_pb_mpl_2_...`).


## Reference
This oTree app is based on the script by Felix Holzmeister, who provides the Multiple Price List task proposed by Holt / Laury (2002), American Economic Review 92 (5). 
This Publication has to be cited: Holzmeister, F. (2017). oTree: Ready-Made Apps for Risk Preference Elici- tation Methods, Journal of Behavioral and Experimental Finance 16, 33-38.The script has been heavily customized.

Origninal Files from F. Holzmeister for download:
- [License](http://www.holzmeister.biz/downloads/mpl/License.pdf "license")
- [Documentation](http://www.holzmeister.biz/downloads/mpl/Documentation.pdf "documentation")
- [Demo](http://cl-apps.herokuapp.com "demo")
- [Multi-Language Support](http://www.holzmeister.biz/downloads/mpl/Multi-Language%20Support.pdf "multi-language support")
- [Automated Testing](http://www.holzmeister.biz/downloads/mpl/Automated%20Testing.pdf "automated testing")