A student records the initial length l, change in temperature $\mathrm{\Delta T}$ and change in length $\Delta l$ of a rod as follows:
 

S.No.	$\mathrm{\Delta T}\left({ }^{\circ }\mathrm{C}\right)$	I(m)	$∆I\left(m\right)$
1 2 3 4	2 1 2 3	10 10 20 10	$4\times {10}^{-4}$ $4\times {10}^{-4}$ $2\times {10}^{-4}$ $6\times {10}^{-4}$

If the first observation is correct, what can you say about observations 2,3 and 4 .