Is a way to achieve comparability between the experimental and control groups by assigning the same numbers of people to the two groups after placing them in categories of interest.

True Experimental Research Design.

Explanation:

Experimental Research have three types of design:

Pre-experimental research design, It is the simplest form of research design under which different groups are kept under observation to see the result over cause and effect of experiment.True Experimental research design, out of all three it is the most accurate form of research design which rely upon statistical analysis of controlled group and experimental group.Quasi-experimental research design, it is similar to experimental research with the difference of assignment assigned to two control group.

Because global warming is occurring and there’s no ice for the polar bears to live on.