Analysing data---- Insignificant results???

This week I am done with key in the data for my study. To be exact, I was not the one who keyed-in all the marks and responses (for the questionnaire). I hired a student to do the job. As far as sorting the instruments in the study is concerned, I did it myself. Also, transcribing part I am still doing it. Some of the results of the study showed insignifcant results. It worried me badly. Finding how to report the findings, gave me some ideas that there were few things that might contributed to the results. I obtained the ideas to jusitfy the insignificant results when I I goggle it. Though many of the websites I found discuss more on the significant results. However, one of the articles wrote that in reporting for insignifcant results, a researcher may look at the following:

(i) inadequate or biased sample. I think i can include this because one of my treatment groups were diploma holders while two other groups were matriculation and STPM holders
(ii) incorrect methodology. I might take a look at this. Perhaps I needed to compare which part of the questions did students score more.
(iii) design flaw.
(iv) errors in measurement. Maybe there's a point to consider
(v) data collection analysis
(v) unforeseen circumstances. I remembered that students were instructed to take the posttest after they sat for their final exam paper. Maybe there were under pressure having had their paper before the posttest was administered.

For whatever reasons in obtaining the insignificant results, I need to justify thoroughly of why it happened. Again, this has to be checked with previous literature. What others had to say and what they found (Like a CSI investigator). It's a challenge for me. I have already had some justifications at hands, yet, as I told, I need to back-up with relevant literature. Next week I'll be going to see one of my supervisors. Maybe I can discuss the results with him... Ya Allah I hope I can handle this well.