Random sampling
Also called: Simple random sampling · Topic: Economic Data: Census, NSS, Surveys and Statistical Tools · NCERT: Class 11, Ch 2 "Collection of Data"; Class 11, Ch 8 "Use of Statistical Tools"
Meaning
Random sampling picks a sample so that every unit in the population has the same chance of being chosen. Random does not mean careless or haphazard. It follows a strict rule of equal chance. It needs a sampling frame, which is a full list of the units. Selection is then done by a lottery, a random number table or a computer.
Example
A study looks at how a rise in petrol prices affects the 300 households of a locality. All 300 names go on slips, the slips are mixed, and 30 are drawn one by one. Every household had the same chance of being picked.
Don't confuse with
- Non-random sampling: here the investigator picks units by judgement, convenience or quota, such as nearby or known households. Units do not have equal chances, so bias creeps in.
Related concepts
- Census
- Sample survey
- Population
- Sample
- Representative sample
- Population parameter
- Non-random sampling
- Sampling frame
- Lottery method
- Random number table