Product review (3 stars): Not very well calibrated, even between inside and outside temperature, but OK for price.
The price is OK. They will JUST serve the purpose.
However, I should have read the reviews! Is seems the 2+ degree error between indoor and outdoor temp. is systemic . . . just as the picture shows . . .  No wonder the fellow looks unhappy :-(

Note also, that below 14F (-10C), the indoor temp simply says Lo.  Outdoor was still going at -8F.

I ordered 3.
True temp (against a good scientific mercury thermometer)  reading dead on 19C = 66.2F
Item  Indoor  Outdoor  Delta-I  Delta-O  Delta-I-to-O
  1  66.2  68.8  0.0  2.6  2.6
  2  67.1  68.6  0.9  2.2  1.5
  3  68.0  69.8  1.8  3.6  1.8
I will mark them as such.  They will then do the job.
Though not well calibrated, the CHANGE in temperature they measure seems OK.
(i.e.  At a lower calibration temperature each were all showing comparable differentials to those shown at 66.2F)

The humidity readings had a spread of 4%.  I do not know the true value.