... do you have any kind of criteria for deciding when to give up on failed lab ideas? I know there are some things that WILL work given huge amounts of time and energy, and with these you have to decide whether it's worth it, but for me it seems like the last two years have been one long string of obstacles which I've been trying to overcome. I'm so gullible - every time I make a modification to my experiment I think 'that'll do it', but it never does... I wish someone could just tell me 'on the three-hundredth modification your experiment will work', but the way things are there's no end in sight!!!

...and there's always the strong possibility that there is more than one thing wrong! We have to follow the rule of changing one variable at a time, so we're fighting a losing battle. Just because a certain modification didn't fix the problem a week ago doesn't mean it won't this week - do you know what I mean?

There's not definitive answer for this one. The only possible answer I can give is to talk to your supervisor. It also depends on your project. If you're CASE funded, then your goals are very specific and you need to concentrate on a very small area (which sometimes feels like you're flogging a dead horse). The one thing I was told is that a thesis isn't all about experiments that did work, they're also about the one's that didn't and you are adding to the pool of knowledge with experiments that didn't work because in the future peoiple will see which reactions don't give the best results, i.e. research.

Although must quickly add, if I wrote my thesis soley based on all the reacitons that didn't work I'd have enough results for a thesis in about 6 months! (Last year was a pain to try and get any results)