Re: [galaxy-user] Quality report

2013-11-06 Thread Ido Tamir
Please be more specific about which quality of what gets reported.
Why do you think its important to reduce the difference between mean and median?

best,
ido

On Nov 6, 2013, at 4:50 PM, Benjamin Osei-agyeman benjy_o...@yahoo.co.uk 
wrote:

 Hi,
 After obtaining a quality report in galaxy I found out that there is a 
 difference between the mean and median at each cycle. How can this difference 
 be reduced using galaxy?
 
 Thanks in advance
 Benjy
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Re: [galaxy-user] Quality report

2013-11-06 Thread Benjamin Osei-agyeman
Hi, 

The report was obtained after running fastqc on my data. However after looking 
at the report statistics, the
Quality is not good in the Per Base Sequence Quality and there is a difference 
between the mean and median at each cycle. How can the quality be improved? And 
why is there a difference between the mean and median in the fastqc report at 
each cycle?


Benjy 
 
 

 
 
 
 
 From:
 
 Benjamin Osei-agyeman benjy_o...@yahoo.co.uk; 

 
 To:
 
 Ido Tamir ta...@imp.ac.at; 

 
 Cc:
 
 galaxy-user@lists.bx.psu.edu; 

 
 Subject:
 
 Re: [galaxy-user] Quality report 

 
 Sent:
 
 Wed, Nov 6, 2013 5:31:22 PM 

 
 

 The report was obtained after running fastqc on my data, I found out that the 
quality of the report is not good and that the mean and median are different at 
each cycle. Please how can the difference between the mean and median be 
improved as well as improving the overall quality 
 
 

 
 
 
 
 From:
 
 Ido Tamir ta...@imp.ac.at; 

 
 To:
 
 Benjamin Osei-agyeman benjy_o...@yahoo.co.uk; 

 
 Cc:
 
 galaxy-user@lists.bx.psu.edu; 

 
 Subject:
 
 Re: [galaxy-user] Quality report 

 
 Sent:
 
 Wed, Nov 6, 2013 4:38:15 PM 

 
 

 Please be more specific about which quality of what gets reported.
Why do you think its important to reduce the difference between mean and median?

best,
ido

On Nov 6, 2013, at 4:50 PM, Benjamin Osei-agyeman benjy_o...@yahoo.co.uk 
wrote:

 Hi,
 After obtaining a quality report in galaxy I found out that there is a 
 difference between the mean and median at each cycle. How can this difference 
 be reduced using galaxy?
 
 Thanks in advance
 Benjy
 ___
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 Galaxy User list should be used for the discussion of
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 please use the interface at:
 
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 mailing lists use the unified search at:
 
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Re: [galaxy-user] Quality report

2013-11-06 Thread James Taylor
On Wed, Nov 6, 2013 at 12:54 PM, Benjamin Osei-agyeman 
benjy_o...@yahoo.co.uk wrote:

 The report was obtained after running fastqc on my data. However after
 looking at the report statistics, the
 Quality is not good in the Per Base Sequence Quality and there is a
 difference between the mean and median at each cycle. How can the quality
 be improved?


Is the quality poor across the entire read, or just at one end? You can
improve overall quality in two ways. By filtering out lower quality reads
(the Filter by Quality tool or Filter FASTQ tool) or by trimming a portion
of the reads (the FASTQ trimmer tool).

It is important to understand that these tools work by throwing away data,
you can't improve the overall quality of reads you already have. The FASTQC
tool is telling you about the quality of your sequencing experiment. The
only way to improve the overall quality is to do the experiment again.


 And why is there a difference between the mean and median in the fastqc
 report at each cycle?


It means your quality score distribution is skewed. This is not necessarily
a concern.


--
James Taylor, Associate Professor, Biology/CS, Emory University
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