Hi to all! I am doing my PhD in the field of psycholinguistics and I have designed a specific experimental design for which my supervisor agreed. However, I noticed that my experiment had a significant flaw and I did not take into account an important factor, which would lead to our results not being so valid. Anyway, I managed to re-design the experiment taking into account thιs confounding variable. Of course I am going to send the new experimental design to my supervisor. However, I am afraid that he will consider that I have not read the literature well and therefore I am not a good researcher since I did not find this confounding variable earlier (I was ready to proceed to data collection!). I am very puzzled about how to deal with this issue...Any suggestions would be more than welcome. Thank you in advance!

So your supervisor didn't notice the flaw either and agreed with your original plan? It is better to fix a flaw early that have to explain it later or worse repeat the data collection. If it is a real flaw your supervisor will be relieved and impressed you found it now and not after the data collection. It is easy to overlook thing so don't worry, just be happy you found it

I argree with rewt. well done on noticing the error. Explain to you supervisor what exactly happen and why it need to be changed. They should be fine with it !