# Confusing quality plot

**URL:** <https://forum.qiime2.org/t/confusing-quality-plot/27301>\
**Category:** User Support\
**Tags:** quality-filter, quality\
**Created:** [August 3, 2023, 9:42pm UTC](https://forum.qiime2.org/t/confusing-quality-plot/27301 "2023-08-03T21:42:55Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Zubidiego](https://forum.qiime2.org/letter_avatar_proxy/v4/letter/z/f19dbf/32.png) [@Zubidiego](https://forum.qiime2.org/u/Zubidiego)\
**Post date:** [August 3, 2023, 9:42pm UTC](https://forum.qiime2.org/t/confusing-quality-plot/27301/1 "2023-08-03T21:42:56Z")

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Hello everyone!  
I am starting to work with a set of 155 samples of V4 region of 16s rRNA that was sequenced using Illumina. I impoted all my data and reached the quality scores plot using QIIME2 2023.5 in conda, but it seems that the sequences are a little weird. I have samples that go from 8784 to 2691122. What do you think abour this? It could be a problem with sequencing or with the creation of the libraries? I am worried because its all the work for my masters degree. Can i keep wprking with this?

Thanks a lot!

Diego

 ![image](https://forum-qiime2-org.s3.dualstack.us-west-2.amazonaws.com/original/3X/9/e/9efd9b88c753c282700fb4f159227378cfc6d80f.png)

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**Author:** ![colinvwood](https://forum.qiime2.org/user_avatar/forum.qiime2.org/colinvwood/32/17303_2.png) [@colinvwood](https://forum.qiime2.org/u/colinvwood)\
**Post date:** [August 3, 2023, 10:50pm UTC](https://forum.qiime2.org/t/confusing-quality-plot/27301/2 "2023-08-03T22:50:59Z")

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Hello @Zubidiego,

Are you confused about the quality distributions, or the number of sequences assigned to samples?

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**Author:** ![Zubidiego](https://forum.qiime2.org/letter_avatar_proxy/v4/letter/z/f19dbf/32.png) [@Zubidiego](https://forum.qiime2.org/u/Zubidiego)\
**Post date:** [August 3, 2023, 11:06pm UTC](https://forum.qiime2.org/t/confusing-quality-plot/27301/3 "2023-08-03T23:06:48Z")

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I am confused about the quality distributions, i've never seen quality graphs like these ones.

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**Author:** ![colinvwood](https://forum.qiime2.org/user_avatar/forum.qiime2.org/colinvwood/32/17303_2.png) [@colinvwood](https://forum.qiime2.org/u/colinvwood)\
**Post date:** [August 3, 2023, 11:15pm UTC](https://forum.qiime2.org/t/confusing-quality-plot/27301/4 "2023-08-03T23:15:12Z")

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Hello @Zubidiego,

I believe that these are referred to as binned quality scores and that newer illumina sequencers output them. You can search on this forum about the topic, there are a few discussions.

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**Author:** ![system](https://forum-qiime2-org.s3.dualstack.us-west-2.amazonaws.com/original/3X/2/1/21af5fe23cb6f4579467c66a9ed94e55274ca7bd.svg) [@system](https://forum.qiime2.org/u/system)\
**Post date:** [September 4, 2023, 5:15am UTC](https://forum.qiime2.org/t/confusing-quality-plot/27301/5 "2023-09-04T05:15:44Z")

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