How can I know if the RNA-Seq data is stranded or unstranded?
If you are interested in using the stranded data in STAR Count gene expression output, you can make a guess by comparing N_ambiguous: if a stranded type has a much lower number of N_ambiguous compared to the other stranded type and the unstranded count, it is a good indicator of a stranded library being used. Please note that knowing a library is prepared by a stranded-enabled RNA-Seq kit does not necessarily guarantee the resulting library is stranded. In addition, data of different strandness can not be compared to each other directly.