Introduction

If you are driving a car and want to know your speed, you do not have to watch the speedometer continuously. It is sufficient that you monitor the continuously indicated velocity by an occasional glance, and that is “Sampling”. Likewise the continuously changing voter opinion of political parties is sampled every few years by an election and the composition of the congress is then fixed for the following term of office. Stock market quotations are set every working day, and the temperature of a sick person is checked several times per day.