What is the difference between population data and sample data in statistics?

For some of my hw problems my prof asks for the answer for both population data and sample data. What is the difference and how to I calculate them differently

What is the difference between population data and sample data in statistics?
The population is the ENTIRE population: For instance if there are 450 students in your class to get the population data you would have to ask all 450 students.





Most of the time this isn't practical, so you select a representative sample and extrapolate that to the whole population.


The difference is in the mean used. You can never get the population mean without measuring the entire population, so you use μ - which is the expected value E(x).


The sample mean is ˉxˉ (which is called x bar, couldn't quite get the symbol) which is the average of the sample.





In terms of the math used this is a very good website to explain:


http://www.chem.utoronto.ca/coursenotes/...