Obtaining Unbiased Contingent Values: Further Tests of Entreaties to Avoid Hypothetical Bias Thomas C. Brown, Icek Ajzen, and Daniel Hrubes

The Hypothetical Bias may come from: over-estimate. ignore their budget constraint try to pay for ‘free riders’ use their vote to indicate whether or not they think such a referendum should be held for real.

Introduction Test method (similar to budget constrain reminder) to correct hypothetical bias Generally the method instructs respondents that when responding WTP, they respond it as if it were real payment.

Method to correct hypothetical bias “reminder” remind respondent clearly that please response as if you are really paying “cheap talk” Instruct respondent that there is the hypothetical bias, discuss about it and remind them they should self-correct for it

Discussion The Cummings and Taylor script is long and difficult to use on the phone or in the mail The Loomis script is short and did not educate about the hypothetical bias The testing has been conducted with the students at the University of Massachusets

Results from experiment

Discussion (con’t) Only further research will determine whether the script can be shortened without loss of impact. If further tests continue to show that the cheap talk script helps remove bias at all but insignificant small (e.g., $1) payment amounts, but works extremely well at higher payment amounts If additional research shows that the script can be shortened in length without loss of effect, it would not appropriate to delay its application to dichotomous choice contingent valuation.

Conclusion The script worked well whether the vote was open or secret at higher payment levels, but inadequately corrected the bias at a lower payment level

Group members Mr. Pornpoj Roger Sangsuchat Ms. Saranporn Rungreangsri Ms. Tanyathon Phetmanee