How Accurate Are Digital Thermometers?

I wanted to know my temperature, so I would know when I have a fever.  I was also curious how my temperature compares to "normal" people.  

But first, I had to figure out how accurate my digital thermometer is.

Accuracy is how close a measurement is to the true value; precision is how much variability there is in repeated measurements.  The thermometer says it is accurate to within +/- 0.2 F, but I have no way to test that because I have no other measurement of my temperature to compare it with.  I can test the precision by taking multiple readings in a row.  This usually yields the same number, indicating that the precision is very good (i.e. low variability).  However, sometimes, depending on how I hold the thermometer, the readings can vary by as much as 0.4.

What is my normal temperature?  

To test this, I took my temperature over 10 days in April, 2024.  I took 48 readings, a total of 3-4 for each hour of the day.  For each reading I lay down for a minute and then put the thermometer in my mouth, as far back under the tongue as possible.  Each reading took 90-120 seconds, so this effort included more than an hour of total time spent taking my temperature.

My average temperature is 97.4, almost a full degree less than the widely-quoted population average of 98.2.  Standard deviation is 0.6 degrees, so 68% of the time my temperature is between 96.8 and 98.  This variability include any precision variability in the thermometer.

My temperature usually reaches a minimum in the morning, rises to a maximum is in late afternoon / early evening, and then begins to fall before bedtime.  My highest temperatures were recorded after exercise, doing chores, eating a warm/fatty dinner, and lying in the sun.  Minimum temperatures were recorded lying in bed, after exercise, and after breakfast.  

Predicting Plant Phenology

Plants in the Southwestern deserts respond to water availability and temperature:

Map from AHPS Precipitation Analysis from January and February

NM is doing good on water so far this year!

Growing degree day map from PNWPest.org

On average NM is about 6 growind degree days (GDD) behind 2014, but 11 days ahead of 2013 and 6 days ahead of normal.

Two views on global warming "standstill"

A flash animation from wattsupwiththat:

The view from from Skeptical Science:

Western Temperature and Precipitation

from Cliff Mass.

Pleistocene Climate Change Context

A roadmap of the last 50,000 years helps put the modern global warming in context:

This awesome graph, and many others, can be found here. Includes a good discussion of the Eemian interglacial and other interglacials in comparison with the modern Holocene.

Best comparison of world temperature trends

from: Wood for Trees

Wavelet Coherence Analysis!

I've started using a cool Matlab program that generates a 4-dimensional power spectra for any time series. A normal power spectra is averaged over an entire dataset, but this technique, called Wavelet Coherence Analysis using a sliding "window" to examine power spectra continuously over the entire series. Of course, for longer and longer wavelengths, the sliding window necessarily becomes larger and larger, until wavelengths can no longer be measured on the data. The dark black hemicurve on this diagram shows that limit, and the data greyed out beyond that line is edge-affected power spectra.

The data I chose for this analysis were the maximum daily temperatures for Chapel Hill, North Carolina, in 2010. There are 365 days along the X axis, and various wavelengths ranging from 4 to 64 days along the Y axis. Colors indicate "power" at a given wavelength, for a given time of the year. Significant areas within the hemicurve are circled with a black line.

This analysis shows that there were some 6-day cycles in springtime (near DOY 150) that were statistically significant. Beyond that, not much jumps out: the signal does now have high periodicity. Now I'm looking for better-behaving data.