The most simple version makes use of (number) input fields. The participants enter numbers in the two fields and clicks the button. However, if the number of possible inputs is very large, participants may not like all this typing, and we may use a slider instead.
In the third form the user can decide what input to use: the slider (mouse and arrows) or a text input.
Finally, you can use a calculator without a submit button. This is very users-friendly but has an enormous drawback: we cannot keep track of what decisions the participant is considering. In this version it is quite likely that the participant will look for best responses: fix the production of others and use the slider to find the best response.
and this string is put in a hidden field of the decision form: in this example this hidden field is called
hiddenField1. When the participant makes a decision the value of this hidden field is send along and can be be saved in the database. The string has the form:
-90&30-120&40-150&50 which in this example means that the participants has used the calculator three times this period, the first with the productionother 90 and yourproduction 30, the second time with productionother=120 and yourproduction=40, etc.
Download these four examples in one zip-file. The html files of the four examples are respectively named calculator0.html, calculator1.html, calculator2.html, calculator3.html.