All social sciences use statistics as do allied fields like public speaking and debating. Finding and citing a relevant statistic or poll can add weight or color to your argument. The websites listed in this guide provide a wide range of statistics, many of which you can customize to your specific research topic. There is also a tab on books which define statistical terms and how to compute your own statistics.
Further background on this quote is provided by Stephen Goranson who writes on the Mark Twain Forum in a post dated 31 July 2002: "Twain's Autobiography attribution of a remark about lies and statistics to Disraeli is generally not accepted. Evidence is now available to conclude that the phrase originally appeared in 1895 in an article by Leonard H. Courtney. So Disraeli is not the source, nor any pre-1895 person; merely Courtney. The 1895 article is now available online at: http://www.york.ac.uk/depts/maths/histstat/lies.htm. Courtney may have read Carlyle on statistics (also quoted at this site). Certainly the abuse & misuse of statistics were complained about before 1895." From http://www.twainquotes.com/Statistics.html