PCT_ribosomal base and PCT_intergenic base in standard RNA-Seq

Question

[CY]

I have been using STAR for RNA-Seq alignment.

For alignment QC based on the bam file, Picard indicates a wild range of percentage of ribosomal base (10%-50%) and percentage of intergenic base (10%-50%) across samples. I am not sure if this is normal

I assume the percentage of ribosomal base depends on the RNA selection method and percentage of intergenic base should be relatively low, right?

Can anyone share some insights on this? Thanks