[BioC] cDNA microarray Questions

[michael watson (IAH-C)]

>The correlation coefficients are very low. Is that the normal case? 
>Do I need to delete some poor quality genes before any analysis and 
>what rule should I use? 

Which correlation coefficient are you using?  I regularly see very low pearson correlation coefficients between biological replicates but that can be put down to natural biological variation - no two organisms are the same, right?  BUT if you start seeing low correlations between technical replicates (e.g. replicate samples from the same animal/tissue/organ/whatever) then that indicates that you have a lot of variation in your technology, which is bad.

ON another note, I always find the Spearman Rank Correlation Coefficients to be much higher.

Mick