What was observed
Set the two tubes side by side and one loses its colour sooner than the other.
The observation
The potassium permanganate solution at the higher temperature is seen to lose its colour in less time.
The same solutions, the same volumes, the same nails. Temperature was the only thing that differed, so temperature is the only thing that can account for the difference in time.
The conclusion
As the temperature rises, the rate of reaction rises.
The observation about refrigerators agrees with this — there we are lowering the temperature precisely in order to lower the rate of reaction. On the next page we ask why this happens.