Variability
Selecting a random sample from a population involves randomness, so repeating the sampling would result in different sample data. Interpreting the data in a single random sample should therefore take account of the fact that the sample could have been different.
Effect of sample size
In later chapters, we will describe in much more detail how to use sample information to make inference about an underlying population. At this point, we simply note that:
Calorie intake in UN countries