13.29 Debunking astrology with correlation: The New York Times reported that an officer of the International Society for Astrological Research, Anne Massey, stated that a certain phase of the planet Mercury, the retrograde phase, leads to breakdowns in areas as wide-ranging as communication and travel (Newman, 2006). The Times reporter, Andy Newman, documented the likelihood of breakdown on a number of variables, and discovered that, contrary to Massey’s hypothesis, New Jersey Transit commuter trains were less likely to be late, although by just 0.4%, during the retrograde phase. In contrast, and consistent with Massey’s hypothesis, the rate of baggage complaints at LaGuardia airport increased a tiny amount during retrograde periods. Newman’s findings were contradictory across all examined variables—rates of theft, computer crashes, traffic disruptions, delayed plane arrivals—with some variables backing Massey and others not. Transportation statistics expert Bruce Schaller said, “If all of this is due to randomness, that’s the result you’d expect.” Astrologer Massey counters that the pattern she predicts would only emerge across thousands of years of data.

a. Do reporter Newman’s data suggest a correlation between Mercury’s phase and breakdowns?

b. Why might astrologer Massey believe there is a correlation? Discuss the confirmation bias and illusory correlations (Chapter 5) in your answer.

c. How do transportation expert Schaller’s statement and Newman’s contradictory results relate to what you learned about probability in Chapter 5? Discuss expected relative-frequency probability in your answer.

d. If there were indeed a small correlation that one could observe only across thousands of years of data, how useful would that knowledge be in terms of predicting events in your own life?

e. Write a brief response to Massey’s contention of a correlation between Mercury’s phases and breakdowns in aspects of day-to-day living.

f. If the rate of baggage complaints at La Guardia is correlated with retrograde periods, why might this be a spurious correlation?