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	<id>http://genome.sph.umich.edu/w/index.php?action=history&amp;feed=atom&amp;title=Phred_scale</id>
	<title>Phred scale - Revision history</title>
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	<updated>2026-10-15T15:05:43Z</updated>
	<subtitle>Revision history for this page on the wiki</subtitle>
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		<id>http://genome.sph.umich.edu/w/index.php?title=Phred_scale&amp;diff=720&amp;oldid=prev</id>
		<title>Goncalo: Created page with &#039;A scale commonly used to measure data quality and error rates in sequence analysis. It was popularized by Phil Green&#039;s PHRED base-calling software.   It is defined as:  &lt;math&gt;   …&#039;</title>
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		<updated>2010-03-23T20:17:13Z</updated>

		<summary type="html">&lt;p&gt;Created page with &amp;#039;A scale commonly used to measure data quality and error rates in sequence analysis. It was popularized by Phil Green&amp;#039;s PHRED base-calling software.   It is defined as:  &amp;lt;math&amp;gt;   …&amp;#039;&lt;/p&gt;
&lt;p&gt;&lt;b&gt;New page&lt;/b&gt;&lt;/p&gt;&lt;div&gt;A scale commonly used to measure data quality and error rates in sequence analysis. It was popularized by Phil Green&amp;#039;s PHRED base-calling software. &lt;br /&gt;
&lt;br /&gt;
It is defined as:&lt;br /&gt;
&lt;br /&gt;
&amp;lt;math&amp;gt;&lt;br /&gt;
  PhredScore = -10 log10 (\epsilon)&lt;br /&gt;
&amp;lt;/math&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Thus, a base call that is expected to be correct 99% of the time (1% error rate), would be assigned a phredScore = 20. A base call expected to be accurate 99.9% of the time (0.1% error rate), would be assigned a phredScore = 30.&lt;/div&gt;</summary>
		<author><name>Goncalo</name></author>
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