There is no inferential data. There is inferential statistics which from samples, you infer or draw a conclusion about the population. Hypothesis testing is an example of inferential statistics.

two types is:

1. Descriptive statistics.

2. Inferential statistics.

Why are measures of variability essential to inferential statistics?

Inferential statistics uses data from a small group to make generalizations or inferences about a larger group of people. Inferential statistics should be used with "inferences".

Descriptive statistics is a summary of data. Inferential statistics try to reach conclusion that extend beyond the immediate data alone.