User:Ken McRitchie/sandbox5

Carlson's experiment
Astrology can be quantitatively tested by using blind experiment. The most renowned of these is Shawn Carlson's double-blind chart matching tests in which he challenged 28 astrologers to match over 100 natal charts to psychological profiles generated by the California Psychological Inventory (CPI) test. When Carlson's study was published in Nature in 1985, his conclusion was that the predictions based on natal astrology in his tests were no better than chance, and that the testing "clearly refutes the astrological hypothesis".

In one of Carlson's tests, success was based on whether astrologers could match the genuine CPI in sets of three CPIs against a natal chart as either their first or second choice. Because the third choices were measured at a rate no better than chance, Carlson concluded that the first two choices were made at a rate no better than chance. In their other test, the astrologers were asked to rate the accuracy (on a scale of 1 to 10) of the same CPIs against the natal charts. Because the responses in the categories of the first, second, and third choices carried over from the chart matching test were no better than chance in this rating test, Carlson concluded that the rating responses were no better than chance.