Why is there a difference between a sample and population mean/standard deviation or a sample and population proportion? how accurately does the "sample" you discussed represent the actual or potential "population" of data? What steps can you take to improve the probability that decisions you make based on the sample will be reliable and valid in the future, in other locations, or with other people?
Why is there a difference between a sample and population mean/standard deviation or a sample and population proportion?
The population mean is the average of all the items in the full population. The sample mean is the average of the subset that you pulled as a sample. The standard deviation of the population is how much variance from the mean is found in the population and the standard deviation of the sample is the amount of variance from the mean in the subset you pulled as a sample. Similarly, the proportion in the population is the proportion in everyone while the proportion in the sample is just the proportion ...
Your tutorial is 330 words in everyday language and discusses how samples differ from populations and some ways to ensure that your results are generalizable to the population.