Correlated Observations Explained

While we’re on a short break between seasons, we’re revisiting some of our favorite episodes from Season 1. This week, we’re re-releasing our debut episode on pheromones and sexy sweat, with some added commentary up front..

Sweaty t-shirt dating parties, sex pheromone dating sites, choosing your dating partner by sniffing them up — wacko fringe fads or evidence-based mating strategies? And what does your armpit stain have to do with your kids’ immune systems, or hormonal contraceptive pills, or divorce rates? 

In this episode, we reach back into the 1990s and revisit the scientific paper that started it all: The Sweaty T-Shirt Study. They bring a sharp eye and open mind, critically examining the study and following the line of research to today. Along the way, they encounter interesting statistical topics – including correlated observations, within-person study design, and bar chart blasphemy – with a short, surprising detour into Neanderthal sex. 

Statistical topics

• Bar charts 
• Correlated observations
• Cherry-picking
• Data and methodological transparency
• Multiple testing
• Post-hoc analyses
• Unit of observation / unit of anaysis
• Within-person study design

Methodological morals

“Repeat after me: Bar charts are not for numerical data.”

“Those who ignore dependencies in their data are destined for flawed conclusions.”

References

• Nuzzo, R. Ah, Love at first whiff. Los Angeles Times. May 19, 2008.
• Papamarko, S. Pheromone parties attempt to match singles by scent. Yahoo!life. April 12, 2012.
• Sainani, K. Stone Age Gene Swap. Stanford Magazine. November/December 2011.
• Aldhous, P. Darling, You Smell Wonderfully Different. New Scientist. 6 May 1995.
• Wedekind C, Seebeck T, Bettens F, Paepke AJ. MHC-dependent mate preferences in humans. Proc Biol Sci. 1995; 260(1359):245-249. doi:10.1098/rspb.1995.0087
• Hedrick P, Loeschcke V. MHC and mate selection in humans?. Trends Ecol Evol. 1996;11(1):24. doi:10.1016/0169-5347(96)80237-0
• Wedekind C, Seebeck T. Reply from C. Wedekind and T. Seebeck. Trends Ecol Evol. 1996;11(1):24-25. doi:10.1016/0169-5347(96)81061-5
• Wedekind C, Füri S. Body odour preferences in men and women: do they aim for specific MHC combinations or simply heterozygosity?. Proc Biol Sci. 1997;264(1387):1471-1479. doi:10.1098/rspb.1997.0204
• Havlíček J, Winternitz J, Roberts SC. Major histocompatibility complex-associated odour preferences and human mate choice: near and far horizons. Philos Trans R Soc Lond B Biol Sci. 2020;375(1800):20190260. doi:10.1098/rstb.2019.0260

Kristin and Regina’s online courses: 

Demystifying Data: A Modern Approach to Statistical Understanding  

Clinical Trials: Design, Strategy, and Analysis 

Medical Statistics Certificate Program  

Writing in the Sciences 

Epidemiology and Clinical Research Graduate Certificate Program 

Programs that we teach in:

Epidemiology and Clinical Research Graduate Certificate Program 

Find us on:

Kristin -  LinkedIn & Twitter/X

Regina - LinkedIn & ReginaNuzzo.com

• (00:00) - Introduction
• (06:09) - Conclusion
• (06:16) - Breaking Down the Original Sweaty T-Shirt Study
• (06:16) - Study Design Flaws and Data Transparency Issues
• (06:17) - Media Reactions and the Study’s Public Impact
• (06:26) - The Pill's Influence on Scent Preferences
• (06:30) - Analyzing the Study's Questionable Results
• (06:30) - Other Studies and their results
• (06:34) - Overstated Conclusions and Wandering Discussions
• (06:35) - Pheromone Dating Parties
• (06:39) - Statistical Flaws: Correlated Observations Explained
• (06:55) - The Science of HLA Genes and Mate Selection
• (07:05) - Pheromone Dating Sites and Genetic Matching