Find the absolute change and the relative change in the following case.
The estimated number of refugees in a part of the world increased from 7.8 million in 2005 to 11.3 million in 2020 .
The absolute change is $◻$ million
(Simplify your answer. Type an integer or a decimal.)

Step 1 ：The estimated number of refugees in a part of the world increased from 7.8 million in 2005 to 11.3 million in 2020.

Step 2 ：The absolute change is the difference between the final value and the initial value.

Step 3 ：In this case, the absolute change in the number of refugees from 2005 to 2020 is the difference between 11.3 million and 7.8 million.

Step 4 ：Let's denote the initial value as $initial\mathrm{\_}value=7.8$ and the final value as $final\mathrm{\_}value=11.3$.

Step 5 ：Then, the absolute change can be calculated as $absolute\mathrm{\_}change=final\mathrm{\_}value-initial\mathrm{\_}value$.

Step 6 ：Substituting the given values, we get $absolute\mathrm{\_}change=11.3-7.8=3.5$.

Step 7 ：Final Answer: The absolute change is $\boxed{{\displaystyle 3.5}}$ million.