27.1 Introduction: Body temperatures

The average internal body temperature is commonly believed to be \(\mu= 37.0^\circ\text{C}\), a guideline based on data over 150 years old (Wunderlich 1868). More recently, researchers wanted to re-examine this claim (Mackowiak et al. 1992) to see if this benchmark is still appropriate.

In this example, a decision is sought about the value of the population mean body temperature \(\mu\). The value of \(\mu\) will never be known: the internal body temperature of every person alive would need to be measured… and even those not yet born.

The parameter is \(\mu\), the population mean internal body temperature.

However, a sample of people can be taken to determine whether or not there is evidence that the population mean internal body temperature is still \(37.0^\circ\text{C}\).

To make this decision, the decision-making process (Sect. 15.3) is used. Begin by assuming that \(\mu=37.0^\circ\text{C}\) (as there is no evidence that this accepted standard is wrong), and then determine if the evidence supports this claim or not. The RQ could be stated as:

Is the population mean internal body temperature \(37.0^\circ\text{C}\)?


Mackowiak PA, Wasserman SS, Levine MM. A critical appraisal of \(98.6^\circ\)f, the upper limit of the normal body temperature, and other legacies of Carl Reinhold August Wunderlich. Journal of the American Medical Association. 1992;268(12):1578–80.
Wunderlich C. Das verhalten der Eiaenwarme in Krankenheitem. Leipzig, Germany: Otto Wigard; 1868.