Randomness of data
Not only do we usually have little interest in the specific individuals from whom data were collected, but we must also acknowledge that our data would have been different if, by chance, we had selected different individuals or even made our measurements at a different time.
We must acknowledge this sample-to-sample variability when interpreting the data. The data are random.
All graphical and numerical summaries would be different if we repeated data collection.
This randomness in the data must be taken into account when we interpret graphical and numerical summaries. Our conclusions should not be dependent on features that are specific to our particular data but would (probably) be different if the data were collected again.
The more data that we collect, the more accurately our data will reflect population characteristics, but randomness always exists.