Sampling error
The difference between the value of a sample statistic obtained from a sample and the value of a corresponding population parameter obtained from the population is called the sampling error.
(Note that this difference represents the sampling error only if the sample is random and no nonsampling error has been made. Otherwise only a part of this difference will be due to the sampling error.)
The errors that occur in the collection, recording and tabulation of data, errors occur because of human mistakes, are called nonsampling errors.
Maximum error of estimate , the margin error e
For the population mean µ :
For the population proportion p: