True Temperature??

The three Infrared Thermometers shown above are viewing the same object temperature simultaneously UNDER THE SAME CONDITIONS. 

Which reading is correct?

The truth: All are, since the measurement uncertainty for each device is larger than the reading differences between them. The real object temperature, by this measurement method is about 70 Degrees F.

If one takes the average of the three readings, one finds a more precise estimate of the true temperature and the standard deviation of the readings yields a valid estimate of the dispersion among the readings.

For a better understanding of measurement uncertainty, consider the following:

Carpenters, for example follow a mantra of “measure twice - cut once”. However, in practice, if the two measurements differ by a ‘significant’ amount, a skilled carpenter will measure a third time to determine which prior measurement was more accurate, 

What if the third measurement is different again?

This brings one to the subject of “Measurement Uncertainty” that is covered on another page here at: https://grpeacock.blogspot.com/p/uncertainty.html.