Err this doesn't work, this experiment was merely postulated and was never done for real for decades as technically it was animal cruelty (it hardly served any beneficial scientific purpose like find a cure for cancer).
This was merely an extrapolation of an physiological phenomenon, on testing frogs nervous system it was discovered it couldn't perceive a temperature CHANGE if it was slow enough.
However if the water got hot enough it would still jump out as no matter how slow it increased in temperature, it would always reach a point where the frog started feeling uncomfortable and jumped out in self preservation.
It has no scientific basic any more and now only stands as a social analogy that people don't notice danger if it comes slowly enough. In fact people just don't notice it till it's too late, the only way you can boil a frog is if you kill it or immobilise it before going in the water... or put the lid on tight!
Either way, frogs legs are best fried, thye really are quite tasty, just ask a Frenchman or someone from America's Deep South (two regions where frog's legs are delicacies).