The Wall Street Journal has a great blog written by Carl Bialik who is “The Numbers Guy.” Bialik takes on a whole range of ways statistics and numbers are used – misused – and this week, he takes a look at polling numbers.
In this posting, Bialik looks at web sites, many of which are linked to by major news organizations, that do “mash-ups” of polls – that is, combining surveys from various pollsters to produce an average that shows a trend. But Bialik notes: “The basic objection to combining polls is that different surveys, conducted differently, at different times, with different sample sizes, don’t belong in the same stew.” And he quotes a column by Pollster.com co-founder Mark Blumenthal in the New York Times, who says: “If pollsters disclosed more about how their polls were conducted, we would be in a better position to know which polls are likely to be right, and which ones can be safely ignored.”