Expect value: Difference between revisions
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Created page with " The Expect value (E) is a parameter that describes the number of hits one can "expect" to see by chance when searching a database of a particular size. It decreases exponen..." |
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The Expect Value (E) is the number of hits that a person would expect by chance when searching a database. The lower this value is, the higher the Score (S) of the match is. The closer the E-value gets to zero, the better the match is | |||
The lower the E-value, or the closer it is to zero, the more "significant" the match is. | The lower the E-value, or the closer it is to zero, the more "significant" the match is. But another factor that affects the E-value is the length of query. Since shorter ones have a higher chance of occurring in the database, they tend to have a higher E-value.<ref>National Library of Medicine, BLAST Frequently Asked Questions [online], available at: &amp;amp;amp;amp;amp;amp;lt;http://www.ncbi.nlm.nih.gov/blast/Blast.cgi?CMD=Web&amp;amp;amp;amp;amp;amp;amp;PAGE_TYPE=BlastDocs&amp;amp;amp;amp;amp;amp;amp;DOC_TYPE=FAQ#expect&amp;amp;amp;amp;amp;amp;gt;, [accessed 20/Oct/2013]</ref> | ||
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'''REFERENCES'''<br> <references /> | '''REFERENCES'''<br> <references /> | ||
<ref>National Library of Medicine, BLAST Frequently Asked Questions [online], available at: &amp;amp;amp;amp;amp;lt;http://www.ncbi.nlm.nih.gov/blast/Blast.cgi?CMD=Web&amp;amp;amp;amp;amp;amp;PAGE_TYPE=BlastDocs&amp;amp;amp;amp;amp;amp;DOC_TYPE=FAQ#expect&amp;amp;amp;amp;amp;gt;, [accessed 20/Oct/2013]</ref> | <ref>National Library of Medicine, BLAST Frequently Asked Questions [online], available at: &amp;amp;amp;amp;amp;amp;lt;http://www.ncbi.nlm.nih.gov/blast/Blast.cgi?CMD=Web&amp;amp;amp;amp;amp;amp;amp;PAGE_TYPE=BlastDocs&amp;amp;amp;amp;amp;amp;amp;DOC_TYPE=FAQ#expect&amp;amp;amp;amp;amp;amp;gt;, [accessed 20/Oct/2013]</ref> | ||
Revision as of 20:36, 20 October 2013
The Expect Value (E) is the number of hits that a person would expect by chance when searching a database. The lower this value is, the higher the Score (S) of the match is. The closer the E-value gets to zero, the better the match is
The lower the E-value, or the closer it is to zero, the more "significant" the match is. But another factor that affects the E-value is the length of query. Since shorter ones have a higher chance of occurring in the database, they tend to have a higher E-value.[1]
REFERENCES
- ↑ National Library of Medicine, BLAST Frequently Asked Questions [online], available at: &amp;amp;amp;amp;amp;lt;http://www.ncbi.nlm.nih.gov/blast/Blast.cgi?CMD=Web&amp;amp;amp;amp;amp;amp;PAGE_TYPE=BlastDocs&amp;amp;amp;amp;amp;amp;DOC_TYPE=FAQ#expect&amp;amp;amp;amp;amp;gt;, [accessed 20/Oct/2013]
- ↑ National Library of Medicine, BLAST Frequently Asked Questions [online], available at: &amp;amp;amp;amp;amp;lt;http://www.ncbi.nlm.nih.gov/blast/Blast.cgi?CMD=Web&amp;amp;amp;amp;amp;amp;PAGE_TYPE=BlastDocs&amp;amp;amp;amp;amp;amp;DOC_TYPE=FAQ#expect&amp;amp;amp;amp;amp;gt;, [accessed 20/Oct/2013]