The measurement precision: ±0.4°F within 95°F-107.6°F, and±0.5°F for other temperature ranges.
But, keep in mind, body temperature varies from person to person and fluctuates during the course of the day. For this reason, it is suggested to know one's normal, healthy forehead temperature to correctly determine the temperature.
Different measurement sites(rectal, axillary, oral, frontal, auricular) will give different readings. Therefore it is not a direct correlation to compare the measurement taken from different sites.
An ear (tympanic) temperature is 0.5°F (0.3°C) to 1°F (0.6°C) higher than an oral temperature.
An armpit (axillary) temperature is usually 0.5°F (0.3°C) to 1°F (0.6°C) lower than an oral temperature.
A forehead (temporal) scanner is usually 0.5°F (0.3°C) to 1°F (0.6°C) lower than an oral temperature.
Other issues that can affect the forehead temperature are sweat, air temperature, hair, if a person's head has been covered.