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QuestPlusHandler does not return parameter estimate


I am trying to implement a QuestPlus staircase in my study:

 # create the staircase handler
 staircase =, intensityVals=[3,6,9,12,15], thresholdVals=[.75], slopeVals=[.2,.4,.6,.8], lowerAsymptoteVals=[.5], 
 lapseRateVals =.02, responseVals=[1,0], prior=None, startIntensity=9, psychometricFunc='weibull', stimScale='linear', 
stimSelectionMethod='minEntropy', stimSelectionOptions=None, paramEstimationMethod=({'mean'}), extraInfo=None)

and this seems to work.
Then, in accordance with the documentation (, I call upon the estimate of the threshold by:


which gives me the following error:

Traceback (most recent call last):
File “C:\Users\kr17s887\Documents\bachelor_yanis\program\”, line 149, in
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\data\”, line 1598, in paramEstimate
qp_estimate = self._qp.param_estimate
File “C:\Program Files\PsychoPy3\lib\site-packages\questplus\”, line 296, in param_estimate
raise ValueError(‘Unknown method parameter.’)
ValueError: Unknown method parameter.

Any ideas on what I am doing wrong?


Hi @koen_r,
did you “feed” QuestPlusHandler with some data? If you try to get the parameter estimates without at least one trial of fitting it is possible that the param_estimate attribute is not available.
You can see an example script on how to use QuestPlusHandler here: