search for: 2afc

HelpeRs, I have what amounts to a stupid design---entirely my fault, but it seemed like a good idea at the time. Every participant in the experiment receives a series of a two-alternative forced-choice (2afc) pairs generated at random from a pool of items that make up the pairs. The independent variable of interest is the difference in the 2afc pairs on a metric measure to predict 2afc accuracy. For each participant, the 2afc pairs are generated at random (without replacement) from set of ite...

I have would like to use logistic regression to analyze the percentage of correct responses in a 2 alternative forced choice task. The question is whether one needs to take into account the fact expected probabilities for the percentage of correct responses ranges between 0.5 and 1 in this case and how to adjust the link function accordingly in R (see details below). Gabriel Subjects were asked

...compare two psychometric curves, the conventional way is to fit two logistic curves and compare the 75% correct "threshold" values (whatever threshold means). I want to handle the case similar to the budworm example in MASS (glm(SF~sex*ldose, family=binomial)). My basic idea is that the 2AFC forced choice psychometric curve, normally only defined for positive stimuls differences, could conceptually be continued to negative values by mirroring the values at (0,0.5) to get the whole binomial/logistic curve. As far as I can see, the result would be correct if we divide the counts for a st...

...lore, India - http://wiki.centos.org/Events/Dojo/Bangalore2014 - in the month of Nov. I request you to grant `edit` permission to update my homepage - http://wiki.centos.org/DominicGeevarghese - for further followup with speakers/presenters. Thanks in advance. Cheers, -- Dominic Geevarghese 2C7C 2AFC B327 6D12 FB55 29D8 046D A4F6 43EA CB09

Dear R users, I'm struggling with applying a user-defined link function in lmer. For analyzing data of a 2AFC psychophysical experiment, I would like to model my binary data with a logistic function with a lower limit at 0.5 instead of 0. In a previous question this has been described as a halflogit function. To do so I wrote my own link function and would like to submit it to lmer, however this results in...