I have results of expression as Fold change and Z score. The Z score is a negative value while FC is >1.2. I was wondering what should be used FC or Z score. I understand that z score is the deviation from mean value and can be plus or minus.
How were these results produced? It is possible to have a variable with negative Z-score, coupled with a positive fold-change. You could go by |Z| = 1.96 as a cut-off for statistical significance.
You are right I have large negative z score with positive FC. How do I calculate |Z| , I googled it but could not find. So what should be considered FC
|Z| refers to the absolute value of Z. What I mean is, in the absence of any p-values, explore the following as your cut-offs:
- Z > 1.96 & FC > 2
- Z > 1.96 & FC < -2
- Z < -1.96 & FC > 2
- Z < -1.96 & FC < -2
You did not answer my question about how the data was processed, so, I cannot help you further. It is interesting and surprising that you have been presented with data that has no p-values.
Also be weary of whether or not your 'FC' values are linear, natural log, or log [base 2] fold changes.
Good luck.