q-score filtering not working

[sovp]

when I use the --min_mean_q option, no filtering is done. All the reads are just passed to the new file.

[bazante1]

Mean quality score
Read mean qualities are converted to a z-score and scaled to the range 0-100 to make the mean quality score. This means that the read with the worst mean quality in the input set will get a mean quality score of 0 and the read with the best mean quality will get a mean quality score of 100.

See Answer --> #18 (comment)