The above image is an example of interstellar reddening. 
Definitions:
Population Parameter
A numerical characteristic or measure that describes an aspect of a population, such as its mean or variance.
Sampling Distribution
The distribution of probabilities for a certain statistic, obtained from a random sample.
Sample Statistic
A numerical measure that describes an aspect of a sample of a population.
Probability Samples
Samples chosen in such a way that every member of the population has a known, non-zero chance of being included.
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