CorrelationBMJ 2012; 345 doi: https://doi.org/10.1136/bmj.e5407 (Published 15 August 2012) Cite this as: BMJ 2012;345:e5407
- Philip Sedgwick, reader in medical statistics and medical education
- 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
Researchers investigated the association between tea drinking habits and the risk of oesophageal squamous cell carcinoma. A population based case-control study in Golestan province, northern Iran, was performed. Drinking hot tea was found to be strongly associated with increased risk of oesophageal cancer.1
The researchers also investigated the agreement between self reported temperature and the actual temperature at which tea was usually drunk. A sample of 48 582 healthy adults was chosen. Self reported tea temperature was categorised as lukewarm or warm, hot, and very hot. Actual temperature at which tea was usually drunk was categorised as <65°C, 65-69°C, and ≥70°C. The correlation coefficient between self reported temperature and the actual temperature at which tea was usually drunk was 0.46 (P<0.001).
Which of the following correlation coefficients may have been used …