I am trying to run the following regression with ivprobit:
reg1 <- ivprobit(YVAR ~ CONTROL1 |XVAR|INSTRUMENT, data=finaldata)
However, I keep getting the message "Error in chol.default(mat) : the leading minor of order 3 is not positive definite". I saw in some blogs that this could be due to the model being overspecified, but I am just including one control variable at the moment so am not sure how this can be possible.
Does anybody know how to solve this issue? Any help would be greatly appreciated.
Thank you very much!