Tiêu đề Sampling and Estimation (1).pdf ✅

Sampling and Estimation
Population(or Universe) is an aggregate of objects under study in any statistical investigation. In other words, it is the totality of items from which the information is to be recorded. In sampling terminology, population is a larger group from which the sample is selected.  Finite Population: A population containing a finite number of objects is called finite population. For e.g.. The students in a college.  Infinite Population : A population having an infinite number of objects is called infinite population . For e.g. Stars in a sky, fishes in water/ocean.  Existent Population: A population consisting of concrete objects is known as existent population. For e.g. Books in a library.  Hypothetical Population: A population that does not consists of concrete objects or that consists of imaginary objects is called hypothetical population. (The population expected to be )For e.g. The tossing of a coin repeatedly results into hypothetical population of heads and tails. The world hypothetical population is expected to be around 9 billion people.
 A sample is “a smaller (but hopefully representative) collection of units from a population used to determine truths about that population” (Field, 2005)  Why sample?  Resources (time, money) and workload  Gives results with known accuracy that can be calculated mathematically  The sampling frame is the list from which the potential respondents are drawn  Registrar’s office  Class rosters  Must assess sampling frame errors  Three factors that influence sample representative-ness  Sampling procedure  Sample size  Participation (response)  When might you sample the entire population?  When your population is very small  When you have extensive resources  When you don’t expect a very high response