Why should you cite data?
For the same reason you cite journal articles and other resources.
APA style dataset citation:
Hanging paragraph (first line extends to the left)
Name or Title of the Data set (in italics)
Description (in square brackets)
"Retrieved from " DOI or URL
U.S. Department of Health and Human Services, Substance Abuse and Mental
Health Services Administration, Office of Applied Studies. (2013). Treatment
episode data set -- discharges (TEDS-D) -- concatenated, 2006 to 2009 [Data
(example from http://blog.apastyle.org/apastyle/2013/12/how-to-cite-a-data-set-in-apa-style.html)
For more descriptions, see pages 210 through 212 in the Publication Manual of the American Psychological Association, 6th edition - King, B.E.S.T., and Music library call number: BF76.7 .P83 2010
MLA - no specific dataset form, but the following uses rules from anthology, reference work, and electronic materials.
"Title" (in Quotes)
Title of Dataset (in italics)
Year or date
DOI or URL
American Veterinary Medical Association. "Table 1204: Household Pet Ownership: 2006." Statistical Abstract of the United States. 129th ed. Ed. U.S. Census Bureau. Washington D.C.: U.S. Census Bureau, 2010. Web. 14 July 2010. <http://www.census.gov/compendia/statab/2010/tables/10s1204.pdf>.
(example from http://libguides.lib.msu.edu/c.php?g=96245&p=626237)
For more information, see MLA handbook for writers of research papers - King and Art/Arch call number: LB2369 .G53 2009
What to include in a data citation.